SOLVED XB7 modem causing problems with some Android apps - not loading them

After being forced to use Xfinity's new modem, even though I have my own, I had been experiencing certain apps not working/loading on wifi, only on cellular data. I found multiple other posts with the same issue and no solution like this one:

https://forums.xfinity.com/conversations/your-home-network/problems-with-some-apps-on-xfinity-wifi/65d6aa46afe75b042e478953

But this worked for me:

I have a wifi router plugged into the Xfinity modem so I changed its mode from the default router mode to Access Point Mode and bam, all my apps work again.