A Microsoft file hosting and synchronization service.
I've had the same problem. OneDrive has stooped syncing my photos and my "Camera upload" option disappeared from OneDrive.. In my case it happened after I had linked my Samsung account with my Microsoft account. I have fixed the problem by removing Microsoft account from Samsung account. This is how I did it (Samsung S9 / Android10):
- Go to phone "Settings" --> "Accounts and backup" --> "Samsung Cloud" --> (go to the 3 little vertical dots in the right top corner) and choose "Settings" --> "Samsung account" --> "Apps and services" --> "Connected services" and remove the Microsoft account that you use for syncing your OneDrive (in my case I only had one Microsoft account in the list there)
- After removing Microsoft account from Samsung's "Connected services" list (as per step one), go back to OneDrive --> Me --> Settings --> (now the "Camera upload" has appeared again) so click it --> if the "Camera upload account" is blank, the "Camera upload" button will be grayed out so enter your Microsoft account in the "Camera upload account" first --> and finally enable the Camera upload" button.
And after that everything started to work and syncing fine again.