Ensure a site is connected with the Jetpack Complete plan.
The premium theme should activate.
Error banner ""Theme not yet available for this site."
Chrome/MacOS

Team 51 project, tested with multiple premium themes. Also tested in desktop app, where the flow fails differently, but also seems to be related to Jetpack plan changes.
Edited to add: This issue was found on a fresh install of WordPress, freshly connected to Jetpack for the first time.
I just deployed D49976-code, which should address this issue. If @tiffanybridge or @cathymcbride can confirm we can close the issue!
Confirming this works on the affected site.
And I'm not able to repro with a new site either. Closing as fixed!
Most helpful comment
And I'm not able to repro with a new site either. Closing as fixed!