Cannot use the external diff (Mac)

[椋田権吾]

I am using Sourcetree on a Mac.
I have been using Araxis merge as an external diff.

When I press the external diff button, Araxis merge does not launch and I cannot diff. However, I can press the "external diff" button. I can also launch and use Araxis merge independently.

In the settings screen, the external diff tool is grayed out. However, it is grayed out because it was set up previously, so it is still shown that an Araxis merge is specified.
I can't even change the external diff settings because it is greyed out and I can't click on it.
It was working until a few days ago. We do not know the cause.

Can someone please tell me how to deal with this?
I attach a screenshot of the relevant screen and environment.

[椋田権吾 · Accepted solution]

After some more googling, re-installing the application, and messing around, I managed to get it back to a usable state.
As an amateur, I had to open the gitconfig file, check and correct the paths, etc., but I was very nervous.

So, since I have solved the problem myself, I will close this question once and for all.