I am having the same issues! I bought a yearly Lightroom MAS 1TB subscription and it will not let me restore my purchase! Very frustrating. I renewed my subscription in November of 2020 and have yet to be able to use it. Please help.
Since you are asking about Lightroom from the Mac App Store, and not Lightroom for iPhone/iPad, I moved your post over to the correct forum for LR desktop users.
Checking against the account you used to post for help here, I see only a canceled Lightroom Mobile Premium subscription, and no Mac App Store subscription. It sounds like you may be subscribed on Mac using a different Lightroom account/Adobe ID other than the one you've used for the forums here and for LR Mobile. When you try Restore Purchase, does it show any error, perhaps along the lines of "duplicate purchase?" If so, this indicates you are already subscribed with another Adobe ID. In this case, the app is blocking you from subscribing again, so you don't pay twice for the same thing.
I'm going to send you a direct message in a moment with a some additional info.