Almost everything that happened to you happened to me, but I was able to semi-solve it.
Foremost, I haven't played D2 in almost 15 years up until a month or so ago. Coincidentally, I also purchased access to a VPN for the literal first time ever two days into playing again, not having any clue it would ban me. As most already know, I got IP banned, but so was my key. I bought another key, and could not access it, because I was IP banned.
Process:
First I removed the VPN before I bought the second set of keys.
After I got the second set of keys and found out I wasn't able to gain access because of my IP ban, I did these next steps:
Admin CMD prompt "ipconfig /release" [If you don't know what this is, google it.]
"ipconfig /renew"
"ipconfig /flushdns"
Then, I did a hard reset on my router. (As in, I stuck a needle in the back of my router where it has a pinhole saying RESET)
Lastly, I did it again:
Admin CMD prompt "ipconfig /release"
"ipconfig /renew"
"ipconfig /flushdns"
I only did this twice, because I really don't know what the fu#k I'm doing with computers a lot of the time, but it did work, so... You know.
After this, I was able to play on my second key, and after my 14-day ban of the first set of keys lapsed, I was able to play on that too.