Can't log in to the official Plusnet Community forums

I have been a Plusnet subscriber for over a decade. Obviously I signed up as a subscriber in the usual way, and I log in regularly to the main Member Centre to check account details and usage.

I also registered on the official Community Forums website - using a different personal 'username' and password from my main Plusnet subscriber identity, and giving my alternative or backup contact email address which is not with Plusnet..

I have successfully signed in and posted on those official Community forums, although not for a year or more. My older posts are however still there in the forums.

Just recently I had a problem over my Plusnet email account Inbox being full (I have posted separately about this: my emails were archived and rendered inaccessible without much warning). So I thought I would browse the official Community Forums to see whether others had had similar experiences.

I found that I could not sign in to the forums. I know I entered the correct username. I know I entered the correct password (I have a note of it). But the Community Forums webpage would not log me in.

After several unsuccessful attempts I opted to take up the offer of help with a forgotten password. The theory is that you put in the email address used when you originally registered, and Plusnet sends an email with a link that enables you to reset your password......

Well, that's the theory. A popup appeared saying an email had been sent which would enable a password reset.

No email arrived. I tried again - twice - to request a password reset. Twice a popup advised that a 'reset' email had been sent. Nothing.

The problem is not with my own email accounts. When I registered on the Plusnet Community Forums site I deliberately chose a different username, and used my alternative, non-Plusnet email address which I know is functioning normally. Just in case, I have also sought a password reset and provided my Plusnet email address. Nothing there either (although my Plusnet inbox, with all the old messages archived, now has ample space and is working normally).

All of which seems to suggest that (a) there is a problem over signing in to the Community Forums, AND (b) a serious issue over the way Plusnet sends out their emails to the "alternative" contact email address. The system ain't working as it should. Can anyone offer any insight into this, or any advice?