"This Apple ID has not yet been used with the App store"

Hi everyone,

I'm trying to ddl Mojave from the App store as some of my softwares aren't working properly anymore on Yosemite. But I keep getting the same message when I try to connect (the one in the title). I've already done some research and read that it's because I hadn't set a billing and shipping address in my Apple ID account. So I did add this, as well as payment info, but it hasn't fixed the problem... I'm still "locked out" of the App store. If anyone could help I would be very grateful!

Thank you