How were you "not able to post anything"? If you noticed you weren't able to post anything (e.g. got an error message), that was (by definition) probably not shadow banning.
The Lemmy software doesn't have shadow banning, and in fact has a mod log that is very transparent about moderator actions. The modlog doesn't seem to have anything for you.
Was it from a bot or Lemmy itself? If it was from a bot it doesn't really count since admins set that feature up themselves, it's not a part of Lemmy itself.
It's such a lazy bitch move to blanket block vpn users. For anyone intent on causing meaningful harm it's trivial to bypass, so the only ones really impacted are the innocent mass of privacy minded people. Unnecessary hassle for people doing nothing wrong.
It's the most popular instance with questionable politics and moderation and this move pushes people to other instances before they even discover deeper issues there. Most instances have zero issues with VPNs, and it doesn't even matter what is the parent instance of community you're posting to. Which means you can post the same stuff into the same place from almost any other instance using VPN.
I cant post if I have protonvpn running, or at least if Im connected to certain proton servers. It could be along those lines - whatever IP you were coming from might be blocked, probably via cloudflare?