When a multi-platform post fails validation, check six things in this order: connection, caption length, media format, platform fields, links and permissions. The first two cause most failures and take under a minute to check. The error almost always names one platform, so fix that platform's version rather than editing the whole post.
TLDR: Read which platform failed, then check connection, caption limit, media specs, required platform fields, links and permissions, in that order. In Mydrop's data, 98.5% of posts go live first time, and the most common hard failure is an expired connection.
Check 1: is the connection still valid?
Start here, because it is the quickest check and the most common cause. In Mydrop's data on posts published in the 30 days to 16 September 2026, 98.5% went live at the first attempt, and the most common hard failure was an expired platform connection.
If every post for one profile is failing, reconnect that profile. If only one post fails, the cause is somewhere else.
Check 2: is the caption over a platform's limit?
A caption that is fine in one app can be too long for another. These are the caps Mydrop's publisher enforces before sending, except Instagram's 5-hashtag cap, a rule you keep yourself:
| Platform | Limit enforced |
|---|---|
| 2,200 characters, up to 5 hashtags | |
| TikTok | 2,200 characters, hashtags count inside the caption |
| X | 280 weighted characters |
| Bluesky | 300 characters |
| 500 characters for alt text |
A scheduler can reject a caption the app itself would accept, because checks run at send time. If your master caption is long, write a short version for X and Bluesky and keep the long one for the rest.
Check 3: does the media match the platform?
Aspect ratio and file type trip up a lot of posts. A 4:5 portrait image is fine on Instagram and may not suit another channel. A vertical 9:16 video does not fit every placement.
Fix it by exporting a second version, not by cropping inside the composer. If one asset fails on three or more platforms at once, you have a creative problem, not a metadata problem. Go back to the master file and export per platform.
Check 4: are the platform-specific fields filled?
Each network asks for something the others do not. In Mydrop's composer, the Platform Options tab holds these:
- Instagram Stories or Reels: a cover or thumbnail
- TikTok: visibility set to a valid option, usually Public
- Facebook: a post type that matches the attached media (image or video)
- Google Business Profile: a location for the post
- YouTube: a title, and a custom thumbnail if you add one. In our data, the most common warning was a custom thumbnail rejected because the channel was not phone-verified
Open the failing platform's tab and look for an empty required field.
Check 5: are the links and attachments reachable?
A broken link or a media file that has moved in a cloud folder can stop a post. Open every link in a private window. If you pull from a cloud folder, confirm the file is still there and shared. Our guide to fixing broken links and media before scheduling covers the checks.
Check 6: does the account have permission?
Last, look at the account. A page you no longer admin, a business account that was switched to personal, or a role that was removed will fail even a perfect post. Confirm the connected account still has permission to publish, and reconnect through the platform's own login rather than a shared password.
Stop failures before they reach the queue
Failures at send time are expensive, because you often find out about them hours later. Run the same checks earlier. Mydrop's post preview shows each platform's version, and its pre-publish validation flags problems before a post is scheduled. For bulk imports, see what to check when a bulk campaign fails validation.
Next time it fails, read the platform name first
Copy the six checks into your team's checklist and run them in order the next time a post fails. Most posts are fixed by check 1 or 2. To see per-platform problems before you schedule, start free with Mydrop and preview your next campaign.
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