@JentheHumanist Just to let you know Im not affiliate with the development of Jason plugin Paid Membership Pro, I just like helping where I can and mainly with this plugin, Im a user of this plugin and I have a love for wordpress, so I read and help where I can for those using Jasons plugin, I keep up with him on the main dev site. https://github.com/strangerstudios If you register on this site you can follow him and all the updates patches and addon that he comes out with for PMP paid membership pro.
On the other hand looks like the plugin wants to activate its self but the header from the plugin "pmpro-series-master" which is also jasons plugin is activated calling a header as well.
STEP #1. DEACTIVATE pmpro-series-master
STEP #2. DEACTIVATE PMP then Reactivate PMP
STEP #3. if the PMP activates find then...
STEP #4. reactive pmpro-series-master
Lets see what happens.
While the PMP is under development I know Jason depends on us to use this plugin and test it and he will work all the bugs out.
Hang in there, and he will reply to your email , just give him some time, since this plugins release , recently the downloads have grown I have watched it, so people are probably backing up his email.
You know you can get in his PRIVATE members only support to thats priority help and extra perk for code help and etc its $97 bucks
Other than that let me know what happens.