Webhost tells me it is my ISP (Xfinity) which is blocking access to my cPanel

I run a website. In late August the email account of one of my contributors was compromised, resulting in 400k spam emails being sent out before we could lock it down on 09/01/2025. As of 09/10/2025 the issue is completely resolved (including removal from any blacklists). However, since that time whenever I access my hosting account from home, I cannot access the cPanel or Webmail pages unless I use a VPN (or use my cellular network, basically anything BUT being connected to my Xfinity WiFi).

This is also blocks my Mail app from checking the multiple email accounts I use through my hosting provider, once again, unless I have a VPN turned on. 

My web host advises me that it is my ISP (Xfinity) which is blocking this access. They advised to turn off Advanced Security, but that did not resolve the issue.

Please advise.