Diffing a Blueprint does not currently work when looking at previous commits. The diff appears to be looking at pointer files instead of the actual Blueprint files themselves.
When using the Git LFS service, the same warning message appears in the log when right-clicking on a modified Blueprint that has not yet been checked in and selecting the Diff Against Depot option. The Blueprint diff window does not open in this instance.
A message is displayed stating "Unable to load assets to diff. Content may no longer be supported?" In addition, the following warning is added to the log: Warning: The file '../../../../../Unreal Projects/Current Issues/TestGit/Saved/Diff/temp-979aed2724cd364d3a341c7e9dab8271d1fb2f06-NewBlueprint.uasset' contains unrecognizable data, check that it is of the expected type.
The Blueprint diff window appears.
Head over to the existingAnswerHub thread and let us know what's up.