You should absolutely not delete items in the web library unless you want to permanently remove those items from all devices. Deleting is not a troubleshooting step.
If you're having a problem with syncing, see Changes Not Syncing, and provide the requested info in a new thread if you're still having trouble.
If you made deletions that you don't want to keep, you should use Replace Online Library in the desktop app to over. (You may need to temporarily disable auto-sync and restore from a backup first.)
Upgrade Storage
If you're having a problem with syncing, see Changes Not Syncing, and provide the requested info in a new thread if you're still having trouble.
If you made deletions that you don't want to keep, you should use Replace Online Library in the desktop app to over. (You may need to temporarily disable auto-sync and restore from a backup first.)