Thank you all for the workarounds that you have found. I just wanted to provide some steps that were provided to us for this, just in case the above do not work (even though all the steps are similar):
1) Remove the Google account from the phone
2) Clear data and Force Stop Google applications on the phone by going into Settings > Apps > selecting the All area (Google Framework, Google Play Services and similar)
3) Perform ##72786# and let the device reconnect to Sprint services.
4) Re-add the Google account.
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Well I have had this very problem recently. I ended up going ot hte sprint store to have my M9 flashed because everything was totally messed up(No contacts, cound not make calls, kept getting alert that "people" file failed every second literally). Worked fine for a few days after flash and now its doing the same thing people here have said. Google play wont open, I dont get notifications, and contacts list is gone. I did everything yall said to do here. I'm baffled and seriously mad about this. If it wasnt for still paying on this phone and not being able to upgrade for a few more months, I would change. I love HTC. My last 3 phones were HTC. This, this is seriously getting under my skin and loosing faith in HTC's new lines.
I think its the updates that screwed me up. i noticed the pay store pushed and update yesterday when it started. like Google and HTC either are not playing well or something. right now i have rolled back the files and still google play store wont even open. i got a message that said the play store was not installed. boggles my mind since i had to have the play store to even get my apps.
Tnk you for the suggestion, but no. Safe mode does not fix it. Still the same thing. tap the google play app and it doesnt nothing. I do honestly think the clash is with HTC Sense and Android. When my phone acted up before the only way I could get anything to work was when sense failed. I hate that I might have to go back to the sprint store and have them reflash my phone again because i was stuck in a loop when I tried to factory restore it. The restore kept hitting the google play part and kept crashing. To me it seems there is an update, that goes straight to the API and that is the cause of the clash.