After you update the device there are some devices showing problem with play store and google play services.So those getting this problem kindly download the newest ver. of play store from out side market and update it.After that it will shows authentications prblem so kindly wait or connect to wifi then update the play service.my problem solved
In settings > Apps > tap three dots on right hand side upper corner > Reset App Preferences. After that, restart the phone and check if the problem persists.
after update to android 7.. if any one. face.. problem.. u can..factory reset.. it... that will definitely solve.. the play store.. issue..and any..other serious problem