And I mean that literally. I have never done anything with the account. I created it years ago, but I never got around to posting a photo or anything. It's just an account with no activity.
When I try to login, I see this:
> Your account has been permanently disabled because it didn't follow our Community Guidelines. This decision can't be reversed either because we've already reviewed it, or because 30 days have passed since your account was disabled. Learn more about why we disable accounts in our Community Guidelines.
So, it's an issue of community guidelines, so what are those? Presumably this: https://help.instagram.com/477434105621119
Those guidelines are all about content, and of course I didn't post any.
My next thought is maybe someone (like a spammer) took over my account and posted something bad. But I have a strong, machine-generated random password, so that seems unlikely.
So I tried contacting support through the mobile app (since I can't through the web site), and a bot sent me a 5-digit number and asked me to reply with a photo of myself holding a piece of paper with that number. I did that and got no response. (But maybe because the ban is permanent I wasn't supposed to be able to contact support.)