Getting this as well. Is this a provider issue/range ban? That happened to me when posting from PC, but not mobile on data. And I am not giving them my fucking email
I saw someone post on another board that using ublock origin will give you the rangeban notification and turning it off and then resetting cookies will undo it. I use it but I havent had any issues personally so it could be something else.
The "your IP is banned for abuse" message is an automatic, random block based on your threat score. It is assigned to your IP after making a post. You can remove it by getting a single post through from a browser the site considers to be less of a threat.
What 4chan does is analyze a bunch of things when you post. Your browser user agent, many of the sent HTTP headers, how many posts have you made, when was your last post, whether you are posting a new thread or a new post, using an image or not, and many other things I forgot. It then assigns a threat score based on all of those, for example certain combinations of strings in the browser user agent will increase the score while having made a post in the past 15 minutes decreases it. Lower threat score gives you easier captchas, higher ones will give you harder captcha and longer timer blocks. New user sessions (for ex. private browsing) all start with a higher score, the more posts you make the lower the score gets. Plus there are per board and even per thread score requirements (the latter are particularly funny).
The thing that triggers the "your IP is banned for abuse" message is that if your threat score is too high, then the site throws the dice (runs an "if (mt_rand(0,1)) {" call, ie. 50% of returning yes/no) on whether you should be blocked or not. These temporary blocks are set after you post, so you could post fine for a while and then get a random block. They are also paired up with your IP, so if you can push a new post, it will remove the message.
The user agent check is however broken, and keeps assigning Firefox a too high score. So what you can do is to use desktop Chrome to post once, it will then clean the temp block for your IP, and you can post from Firefox again.
Messing with ublock origin may change your browser profile enough to get a new message through the same way, but using desktop Chrome works 100% for me whenever I get the block.
So it's not an actual IP abuse filter, the site just throws the dice on whether it likes you or not.
edit: the spur.us and mcl.io blocks are piggybacked on this system, they are only loaded if the calculated thread score is very high. Then the site runs those. It makes sense because if they ran it on every post, they'd end up sending hundreds of thousands of calls per day.
It's actually a pretty good idea on paper, it's just not set up properly. Or, they had it set up broken intentionally because the error message tells you to by a pass, which bypasses the entire threat score generation.