Synthesia is one of the better AI video tools out there. I've evaluated a lot of them. But the error messages when something breaks are genuinely unhelpful — "Generation failed" tells you nothing about what to actually do.
So here's what's actually going wrong in each case, and how to fix it.
1. Check the Status Page First
This sounds obvious. Most people skip it and spend 40 minutes debugging a problem that's on Synthesia's end.
Go to status.synthesia.io before you touch anything else. Synthesia has had real incidents in 2026 — including a generation and performance outage in April that lasted nearly seven hours. If the platform's degraded, no amount of hard refreshing will fix it.
If the status page shows all green but you're still having problems, then it's local. Move on to the other fixes.
2. Video Generation Stuck or Failed
The progress bar appears, sits there, and eventually either fails or just... keeps sitting there. This is the most common Synthesia complaint.
Hard refresh first. Ctrl+Shift+R on Windows, Cmd+Shift+R on Mac. Not a regular refresh — a hard refresh clears cached state and re-establishes your session. If your connection went stale mid-generation, this usually shows you what actually happened to the job.
The "Something went wrong" error. Generic, I know. Switch to Chrome if you're on anything else, clear your browser cache, and try regenerating. Synthesia's official guidance is Chrome or Edge only — anything else is unsupported territory.
There's also a reset tool at app.synthesia.io/reset that lets you selectively clear local storage, session storage, and cached data without nuking your entire browser history. Worth knowing about.
If it says manual review. Synthesia moderates 100% of generated content. Most videos clear automated checks instantly, but some get flagged for human review. If yours does, do not cancel and resubmit. That restarts the clock and puts you at the back of the queue. Wait up to 24 hours. If it's still stuck, email support@synthesia.io with the video ID.
3. Avatar Lip-Sync Issues
Two separate problems get lumped together here, so let's separate them.
Avatar not moving in the editor preview. This is expected. The editor shows static avatars — the animation only exists in the final rendered video. Not a bug.
Lip sync is actually off in the generated video. This one's real, and it's almost always the script's fault. The avatar's mouth movements are synthesized from the text — the engine is predicting mouth shapes based on phonetics. Feed it unnatural input, get unnatural output.
Fixes that actually work: add commas and periods where you'd naturally pause when speaking. Keep sentences under about 20 words. Spell out acronyms phonetically instead of writing them as abbreviations. If you're using a photo-based personal avatar, make sure the source photo shows the teeth — it gives the engine more to work with.
And frame the avatar closer to the camera if possible. Lip sync accuracy degrades at a distance. Closer framing, more accurate mouth matching.
One specific community-reported issue: Express Avatars in multi-avatar dialogue scenes (particularly "Nelly" and "Jude") have had documented sync problems. If you're hitting that, swap to a different avatar configuration and see if it resolves.
4. Export Not Working
The MP4 download button is missing, grayed out, or does nothing when you click it.
The interactive elements problem. This is the most common cause. If your video has branching logic, quiz elements, or interactive buttons, Synthesia can't export it as a flat MP4 — those features don't exist in a static file format. Your options: embed the video via Synthesia's share link, export as a SCORM package for LMS platforms, or duplicate the video, strip out the interactive elements, and download that version.
For regular videos without any of that? Check your plan limits. Some plans cap total video minutes. If you've hit the limit, new exports won't process.
Subtitle files (.srt and .vtt) are available separately from the three-dot menu next to any video. Not in the main export dialog — it's tucked away, and people miss it.
5. Slow Rendering
Rendering time varies based on two things: platform load and content moderation status.
Automated moderation is fast. Manual review is not. If your video content triggered any flags — certain topics, unusual scripts, restricted scenarios — it goes to a human queue. That can take hours. Resubmitting makes it worse.
Check the status page. If Synthesia's having a degraded performance day, generation slows across the board. Not much to do but wait.
6. Caption / Subtitle Problems
Captions in Synthesia are not something you add after the fact. They have to be enabled before you generate.
If you generate a video and realize captions aren't there, you need to go back into the editor, toggle captions on, and regenerate. There's no way to inject them post-render.
For viewing: the CC button is in the bottom-right corner of the player. Easy to miss. If you sent someone a share link and they're saying there are no captions, make sure they know to click CC.
Burned-in captions — the kind that are permanently baked into the video file — can't be turned off by viewers. If you need viewer-controlled captions, use the CC toggle option, not burned-in.
7. Login and Authentication Errors
Most Synthesia login problems come from sign-in method mismatches.
If you created your account with Google, you need to log in through Google. The email/password login path won't recognize you. Same deal if your company set you up via SAML SSO — that's your IT team's domain, not something Synthesia support can fix from their end.
Account locked after failed attempts? That triggers after five consecutive failures. Use the reset password flow to get back in.
"Invalid Subscription" error on sign-in usually means your subscription lapsed or there's a credentials mismatch between what you're using and what's on the account. Contact support@synthesia.io directly for that one — it's not self-serviceable.
When It's Not a Synthesia Problem
Sometimes the issue isn't Synthesia. It's the browser, the network, or an extension interfering with WebSocket connections Synthesia uses during generation.
Standard checklist: Chrome or Edge only. One tab. No aggressive ad blockers or privacy extensions (or test in an incognito window). Corporate VPN or firewall? Try on a personal connection to rule it out.
If you're running into persistent issues and need an alternative while you sort it out, HeyGen is the other major AI avatar platform with similar feature coverage. We've also compared them directly in HeyGen vs. Synthesia if you're weighing a switch.
Most Synthesia problems are fixable in under five minutes once you know the actual cause. The platform's solid — the documentation around error states just isn't great. Hopefully this fills that gap.
Still stuck? Email support@synthesia.io with your video ID. They're responsive, in my experience.
