Safari web issues

Sorted my problem out by reinstalling Safari via this link Safari 15.0

Check out answer from bryanr14 to nlt05a’s question “ Safari 15.0 Update Issue, macOS Catalina”

I don't know whether this works if you are on Big Sur, but could be worth a try if so.

Sort of the same thing here except it's a credit card account not bank.

No problem logging in via Firefox but Safari just doesn't want to know.