OneDrive Mac App stuck on "Preparing to upload" or "Processing Changes

amaumexia Check if this issue is because you are syncing too many files at once? We have a limitation: Restrictions and limitations in OneDrive and SharePoint - Microsoft Support

1.Perform OneDrive Reset: Reset OneDrive (microsoft.com)

(Perform below steps if step 1 does not resolve your problem.)
 

2. Delete keychain,

MAC by Finder > Go > Go to folder >  ~/Library/CloudStorage/*

Open OneDrive -> Delete items (top right corner button in file explorer)

3. Clear /Users/username/Library/Group Containers
a. Unlink all libraries in OneDrive.
b. Delete the folders xxxx.OneDriveStandaloneSuite and xxx.OneDriveSyncIntegration
c. Delete them from Trash as well.

4. Follow article to clear .DSStore cache: Fix OneDrive sync problems on a Mac (microsoft.com)

Remove DS_Store Files on macOS (microsoft.com)

Clear cache of local machine on MAC by Finder > Go > Go to folder >  ~/Library/Caches > Remove all files/folders

Now navigate to Finder > Computer > Mac HD > Library > Caches > Remove all files folder