microsoft connection problems

We are having trouble with Xfinity connection mainly when it comes to Microsoft.

First, it sarted with Xbox One, then my son got a gaming PC and has intermittent issues with connecting to One Drive. (PC is hardwired) It will work for awhile then suddenly it won't work at all. We have tried a TON of troubleshooting strategies and have changed the modem. It is important to note that the internet connection works well on all of our other devices in the house except his gaming computer and the Xbox. It seems to be a problem with Xfinity and Microsoft working together...maybe security or something but why the sudden inability to connect after nothing was changed?  It continues to keep happening and then suddenly it will work...then it won't.