Starting with Acronis True Image 2018 Update 4 (Build 12510) the OneDrive folder is excluded from backups. In version 10.0.17134, Windows added "Files on demand" technology to OneDrive functionality. This technology saves disk space, using a virtual file system to access the files and folders directly from cloud. Technically, OneDrive folder and its contents is converted from what we know as files and folders into "NTFS reparse points" - special NTFS file system objects, that cannot be backed up by Acronis True Image. It is enough for just 1 element in the OneDrive folder or the OneDrive folder itself to be an "NTFS reparse point", for the entire backup to fail.
Acronis Development Team is working on solution for backing up OneDrive folders. In the meantime, these folders are excluded from backup to ensure backup consistency (both in new and existing backups). Please be aware that even if OneDrive folders are not listed in the list of exclusions, they are still excluded from backup source.
For Acronis True Image 2017 and earlier versions of the product it is recommended to add OneDrive folders to exclusions manually to prevent backup tasks from failing.
After recovering the computer from a disk backup where OneDrive folders were excluded you will need to set up OneDrive from scratch.
Acronis True Image 2019 allows to back up contents of OneDrive via special cloud-to-cloud backup. See Acronis True Image 2019: how to back up Office 365 accounts