A. 1. Check file format: Ensure that the files you are trying to upload are in a supported format. Refer to the app's documentation for acceptable file types. 2. Clear app cache: Go to Settings > Apps > MuseClass > Storage > Clear Cache to remove any corrupted data that may be causing upload failures.

B. 3. Restart the app: Close MuseClass completely and reopen it. Then, try uploading the files again.