I recently made an update to an existing (paid) app I have had published on Google Play for a while. While I was working on the new version, I thought I'd implement the Google Licensing Verification Library. I followed the instructions from Google at http://developer.android.com/guide/market/licensing/adding-licensing.html . Had things working pretty well at this point - when I changed the test response in the Google Play Developer Console I got a different result in my app. Great!
Then I published this new version.
I installed the signed APK (it's a paid app so I didn't want to download it from Google Play) on my phone (had been testing it on that very same device all along). Now things didn't work at all. I got the "Retry" result from the licensing service all the time. I mean for hours. I went back and fiddled with the source code, changed all kinds of things, nothing worked. The Licensing library always timed out (got a "Check timed out." in from the library in LogCat).
I searched everywhere for an answer, but it wasn't until I ran across this discussion ( http://forum.xda-developers.com/showthread.php?t=1566770 ) and read it to it's very final post that I found the solution.
From the above mentioned post:
"I have just had this issue too & deleting the Google Play Application data (Settings, Applications, choose Google Play & press Clear Data ) fixed it for me. Clearing Cache is not sufficient. Ihe only impact I saw of doing this (apart from my App now working again) is that you have to re-accept Google Play T&C etc when you next use that app and my search history had gone."
I did it, it worked, and now everything is back to working!