Problem getting PROCESS for SPSS to work on Mac?

I'm having some problems running PROCESS v 4.0 on my Mac, for SPSS v27.0.
I can get to the stage where I run the Syntax and it looks like it works. But then the PROCESS tab isn't actually available.
There aren't error signs that appear at any stage, so I was wondering if anyone else was having this issue, and whether there are any solutions to this problem?