If it's a platform - specific issue, look for any error messages. They can give you clues. For example, if it says 'content not allowed', then you need to review what you're trying to post. Also, try logging out and logging back in to the app. This can refresh your account status and permissions.
Sometimes, the platform itself might be experiencing issues. Wait for a while and try again later. Also, make sure you're following the platform's posting guidelines and rules.
There could be several reasons. Maybe your account has some restrictions due to violating the platform's rules. Another possibility is a technical issue like a bad internet connection. Also, the app might be having glitches. Check your account status, ensure a stable internet, and try restarting the app.