Hi lordhog,
Try to configure your GUI client to use the "Beyond Compare":
1. Open the "Preferences" menu of the GUI client.
2. Navigate to "External Diff Launcher" and click "Beyond Compare" buttons.
3. Ensure that the "External Diff Command to compare single files"/"External Diff Command to compare single files" fields are set to the correct path for your BCompare.exe file.
4. Try to open one of the collabdiff files that was downloaded from the Web UI.
As a result, the Beyond Compare tool will be opened and you should be able to see the differences of the file versions.
For your references:
https://support.smartbear.com/viewarticle/66421/#externaldiff-preferences
https://support.smartbear.com/viewarticle/66429/
I hope this helps!
