@ analogkid - I also used Safari as the User Agent initially, though I did try others. So it's possible that the site won't recognise Wayfarer's User Agent method as a valid means of accepting the login details, whereas accessing it via a 3rd party seems to bypass the issue of a login directly on the website.

I will try my Windows system (reluctantly) to login to Discogs, and update the thread accordingly.

[UPDATE] - I tried to login using my Windows system but even that is not allowing me access to that site, so I have sent an email to their support and I'll have to wait for their response to find out what happens next!