FLEI,
I had some free time to research this further and found a way to get myself "banned', AND HOW TO REMEDY the problem. I won't go specifically into how to get yourself banned, but basically it is caused by accessing the forum on different ip addresses from different countries within a short period of time... I.E. The forum software thinks that you are a bad character trying to spoof it and it drops a poisoned cookie on your device. That cookie eventually ages off and let's you back on.. While you still have it on your device, all users who try to login from your device are banned. (As you have experienced and described above.) The good news is, there's a way to get rid of it instantly.
To remove the ban you must remove ALL saved cookies for the forum website. THE KEYWORD IN THAT SENTENCE IS **ALL**. The basic "delete cookies" command does not always remove the one which bans you (this is a whole new issue of DELETE based upon versions of CHROME and maybe other browsers too). To do so, follow these steps. I only have Chrome, so if you are using Edge, Safari, or Firefox it might be slightly different.
Open Chrome
Open Settings (click on your Google avatar icon, at top right and then click on Settings )
Click on Site settings
Click on All sites
Click on the magnifying glass and search for phoenix
You will get at least one result, including...
phoenixusarv.com
Click on the trash can beside Phoenixusarv.Com
Click on Delete & reset
..... Now all of the cookies, saved credentials, saved history, and the "you are banned" cookie are gone!
Open the forum. It will ask you to login as if it was your first time to login on this device. It will ask for your userid and password and all should be good.
From what I can tell after reading hundreds of online support discussions the SMF administrators of our forum have an over zealous rule to block international hackers with too broad of a wildcard pattern for IP addresses... It blocks the bad guys and occasionally tags us too.
Larry