I read that resetting your router may create another IP address.
I am not familiar with IPs. Would getting another address causes issues with hardware or
access to other sites?
Maybe another (ex-)member of the forum you are accessing, who also shares the same ISP as you, got banned, then your ISP gave you his old IP address in a very short period of time. [IP addresses are not created. Your ISP gives you one so you can connect to the Internet using it.] The forum may have assumed that you are the banned member, so refused to grant you access. It's not a perfect forum protection rule, but in these fast times, it's a possibility.
As suggested, if it happens again, I would suggest that you power-down-then-power-up your router, as well as clear your browser cookie cache for this forum to start a new login process.
Edited by Dominique1, 24 December 2023 - 02:06 PM.