I experienced the same thing - believe the 'Bundle' edition on the Play store only had an activation code available for a couple of versions of PD (maybe only one?)
When I reset my tablet and tried to find the code in PD15 it was not available and the answer I got from the forum was that the activation code was no longer available unless you had the earlier version of PD still running - if had realised before I would have noted the activation code for future use!! I just assumed it would always be available to purchasers of PD, apparently not!
I just purchased the retail version from the Play store in the end to access all the features, don't think there was another solution.
(apart from re-installing the earlier version just to get the activation code - too much work when PD15 running quite nicely at the moment!)
Director Suite 365
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Microsoft® Windows 10 (64-bit)