I am also having this issue. I am launching a website and can't access my hosting company's portal. Blocked. This happened one day when I was having tech issues and couldn't login. I figured it was blocked for that and should be able to work that out. Nope. I was on the phone for a long time with the hosting company and it was determined that it was a Comcast/Xfinity issue. Went through the level I dance and spent over an hour with the Level II tech. They had no idea why it was happening. Xfi Advanced disabled. I am supposedly on no block lists (other than the Spamhaus PBL that every Comcast residential customer is on). I can hit the site from other places, just not my home.
Frustrated. I am to start working on this website this week from home due to COVID.
Anyone have any other ideas (besides the already great ideas that were tried above)?