Desperate Comcast Customer. VPN frequently disconnects.

Hello,
Comcast seems to be blocking my VPN connection. I've been using it for quite a while and didn't have any issues but about a week ago the VPN started to disconnect very frequently and when connected is very slow. If I'm connected via my iPhone hotspot, the VPN works just fine. I also went to a Starbucks and connected there with no issues. That tells me that is not my computer or the VPN. Nevertheless, I reached out to the tech team that deals with the VPN for my employer and there are no known issues. I have switched modems back and forth and the problem persists. Right now, I'm using Comcast modem. All other computers, streaming devices, and all other devices in my house have no issues at all. My internet speed is close to 2 GIGS. 
Comcast send their technician, and he couldn't find anything. 
Any ideas?  I'm so desperate that I'm thinking switching ISPs.
Thanks in advance!