@tig said:

Your final paragraph is what worries me...
IF you were unable to add files to the Plugins folder then there should be warning messages...
If I fiddle with my permissions to limit them I get error messages and can't continue.
It never let's me think I've installed it OK when I have not...

So whatever subtlety of permission settings you had tricked it into thinking it can work, and that it had worked - it is perplexing 😕

Well, that's exactly why I responded to this thread. It sounded like the OP's problem was the same. No warning, and no effect. The solution is simple, the source of the problem - who knows? Like I said before - no activity in the Ruby console with this error.