Hey, I resolved the issue!
I contacted Namecheap support via live chat, they have been very patient.
Looking at my passenger.log file and everything. Turns out they had to open the default MongoDB port 27017 on their end, no way to do it without support unfortunately.
So it seems you just need to contact them and tell them you need this port opened.
Hope that’s all it takes for you as well. Good luck!