There is an ongoing issue in OneDrive Personal server causing sync failures for some users. OneSync uses a resumable upload API method to upload files. Resumable upload is an important feature. If network connection is interrupted, at next attempt OneSync continues from the point in the file where upload was aborted. Without this feature the whole file would have to be re-uploaded from scratch. Unfortunately this API method currently fails with a server side error “503 Service Unavailable” and a message “Our services aren’t available right now. We’re working to restore all services as soon as possible. Please check back soon”. This situation has lasted for more than two days for many users, myself included. I’ve filed a support ticket for OneDrive team but haven’t heard back from them yet.

I’ve just released an emergency update of OneSync which has resumable upload disabled. Simple upload is used instead. This is not ideal but at least small and medium size files can be uploaded. Files larger than 100 MB require resumable upload API and therefore attempts to upload them continue to fail until the bug is fixed on the server side.

Please update the app.

This issue affects OneDrive Personal accounts only. OneDrive for Business (Office 365) accounts are working fine.