I'm now having the exact same issue as previously described, as others have pointed out it's annoying that this is still happening after several years of it being reported on here and other threads!
I believe as others have said the issue may be that for some reason the broadband order isn't showing as activated on the order tracker, although I've got the router and thankfully the actual internet side of things is all working okay.
I went through the online chat function (before becoming aware of this thread / forum), which was around 2 tedious hours wasted with the operator sending various password resets to no avail. My account was also reset, but after 2 days I registered again as instructed (having to use a different user name) and still no joy, also still getting the same error messages.
I've sent them a message via instagram as suggested the last post from the retired moderator, but no reply. I'm very reluctant to try the online chat or call them up as I think it'll just be the same stock answers!
I think the only way may be to raise an official complaint and hope that it falls with the right department/person who has hopefully some experience of resolving the issue, which is apparently very widespread!
Don't get me wrong I'd much rather have this problem with the account, rather than the broadband itself, but it's still very frustrating when it's something seemingly so simple as just logging in to an account.
I should also add that I was a Vodafone customer until 2 years ago, and switched to BT as they apparently had priority with Openreach FTTP installation appointments at the time, and that was the only way I could get quicker speeds. Never had any service issues with BT, only the increasing costs, which they couldn't match with Vodafone (Ironically the BT Loyalty team did advise the Vodafone have a lot of complaints for poor customer service, but I confidently told them that they'd always been fine for me when I was previously a customer!!)
.png "Moderator (Retired)"){kind=icon}
