The problem might be caused by incorrect settings of permissions to project files (permissions to the files are set for one user, and server works from another user). Please, check your settings.
If the problem will still remain, please, check logs of the project data/logs and also PHP logs.
It’s working now, although I’m not sure what I did to get it working. I didn’t select a specific version of TreoCore as that isn’t mentioned in the installation guide - it just says to install treolabs/skeleton. I also found that I avoided errors by not specifying a version for TreoPIM either - I just ran the Composer statement without a version: