I wrote a reply yesterday, but then seem to have blown it away...
The only way I can imagine this happening is for a previous IP ban to have included an IP which gets recycled, and for you to have received this IP for a period. That's a pretty big coincidence in the timescale involved, but it's all I can think of. I can try checking the ban lists and the logs of hits on them to try to find one that is likely to be in the same ISP block as your current address, but identifying one such might be difficult.
All I can suggest is that if it ever happens again, you contact me from another place, or using a browser or Tapatalk on a mobile phone, and let me know your IP address at the time of failure - then it would be a quick fix.