Anyone recognize this problem registering on forum?

I’ve been contacted by a user that is having trouble registering on this forum. He gets the message

We cannot detect if your account was created, please ensure you have cookies enabled.

Reports having tried different browsers and ISP. I subscribe to a forum hosting service and try not to get involved in the mechanics of administration. If anyone has any insight into this issue, could you post what you did about it please?

I’ve been lurking for some time now, and just made this account no problems, with some degree of ad/track blocking.

From some google-foo, there’s a “known” issue where password managers are auto-completing a hidden password field on account creation that causes this issue.

Otherwise it seems like browser plug-ins or security software can cause this.