I may have a similar problem. I buy the magazine but wanted to read a (premium) article on the keymodelworld website. The site invited me to "subscribe" - special offer for 35.99. So I did, got a subscriber number and password etc and logged on. No joy with the premium article.
Nowhere on the site does it say you need a sub to the magazine. In fact it implies with a sub you can access everything.
So I emailed customer support, got an automated reply saying my query would be dealt with in a couple of days. That was 4 working days ago (OK there is corona virus...) So I wait.
I am decidedly unhappy about the whole business.