Unable to Use Beyond Compare for Merge Conflict

Hi.

I have contacted you about this bug before.  I received a response but am unable to find it.  the suggested fix was a complete reinstall of SourceTree, including deleting all saved settings from my User folder.  I did this but the issue remains.

I have attached two screenshots that show the problem.  In the first, you can see that I have a file with a merge conflict.  The second shows a right-click, which has the option greyed-out.  In my settings, I have Beyond Compare configured as the external comparison tool, and this did work fine but now appears to have stopped.

Can you offer any suggestions how I can get this re-enabled?

Kind wishes ~ Patrick