The method on Windows 10 is a bit different. Here's how to do it:
From here, choose your settings, such as language preferences, color themes, etc.
Reset all settings here and see if this affects your PC backup.
A malware attack can do anything to your PC. Makes you inaccessible to files, steals sensitive information, and in this case prevents you from making your backups. Go through TipsMake's malware removal guide and get rid of malware that can cause backup problems on your Windows PC.
If your storage space is full, it is understandable to encounter backup errors. Whether it is full due to previous backups, system restore, or some other related reason (such as drive failure), unless you eliminate the underlying cause first, you may will not be able to continue with the backup.
Go through this short guide on how to free up storage space on Windows and get your storage back. Once your storage is back to normal, or if there's no problem with it, have a quick read of the Windows backup guide to learn about the best backup methods at your fingertips.
If none of the above methods worked, then a complete reset of Windows is your last hope. When you're done, the PC should be back to working as it should.