It is now May 22, and I'm still having this issue.
Trying to purchase motion graphics plug in for Adobe premiere pro
Your error is not caused by the same issue mentioned in the other thread. I'm looking into this and checking with our Stock Engineering team.
The reason you are getting this error is you have two active Creative Cloud subscriptions. You'll need to cancel one of them as our system has rules against individuals holding two active subscriptions for the same product.
But what you’re trying to buy is a template. A document. Not a plugin at all...