Sometimes, OneDrive cannot sync certain files. To ensure successful synchronization, here are some steps to follow:

1. Check Microsoft store for a OneDrive app that can upload the desired files.
2. Check the file size of the item attempting to be synced. OneDrive has an upper limit of 15 GB per file.
3. Check the types of files synced with OneDrive. Certain audio and video files like .mkv, .raw, .mim, and .vcf are not supported.
4. Remove any unsupported file types from the folder(s) syncing to OneDrive before attempting to sync again.