Thanks Erel,
I think I know what might be the problem with my test devices.
When I created the release apk I changed the apk file version to something else and didn't upload it to Google Play.
However, the version on Google Play should of worked for the guy that downloaded it from Google Play (I haven't given him any new versions).
I am going to be sending a new update file to Google Play in the next day or so, I guess I just have to wait and see if this new version fixes the error.
The devices with the developer account are less reliable.
If I change the 'License Test Response' in my Google Developer console it seems to follow what I choose every time for the developer account.
On other devices it seems to be hit and miss. So I would of thought my developer account was more reliable, and other accounts not being reliable?
Is DontAllow event raised?
Yes it is. (even on the customers app that he purchased from Google Play)
This happened to another customer just before Christmas last year, and a week later it all started to work normal again. (maybe this will work again in a few days)
Seems like other users encountered this issue
I took a look at that link, seems to be the same as what is happening to me. I guess I need to re-upload my apk file with the new changes and see if it fixes my issues.