I found two previously used IP's in the range blocked because spam reasons. The related IP lists were added fairly recently, so they may have worked previously.
IPs used in error messages doesn't match any of the blocked ranges though. If you want to shoot me a PM with the IP's you have trouble with I can look into it further.
Hopefully you were greeted by a message such as this:
Your IP has been marked as a spam host. If you believe this is in error please message a global moderator. You might also try Discord: https://discord.gg/uaY8akC
If not, it may be an older block that hasn't had it's message updated.
These blocks are all manual. Until the forum software gains some form of automated spam list protection, the lists will remain manual based (so may become outdated). Given the level of spam that has been reduced by aggressively blocking IP ranges lately (and yes, I have been nuking VPN hosts if they host spam bots), the IP block list is only going to grow larger, not smaller. Again, PM's will help with IP's being blocked as I might be able to weed out false positives.