Recientemente he realizado un restablecimiento de datos de fábrica en mi dispositivo y ahora la tienda de juegos no funciona. No se está descargando ninguna aplicación

Lo intentaré en la oscuridad. ....

SI las aplicaciones de Google (incluyendo la configuración de Google, WhatsApp, youtube, etc.) en general no están funcionando/están desaparecidos (tal vez incluso esté tratando de readquirirlos),

y/o ajustes IF > cuentas y sincronización ya no muestra su cuenta de Google y no puedes simplemente añadirlo.

ENTONCES Puede que sepa lo que está pasando (por experiencia personal, también en GB)....

Your problem may be that Google doesn't recognize your phone without the Google apps and *especially* without the Google account it expects to be on/associated with that phone. This despite that your device's ID #s haven't changed.  (pretty sure this is a safeguard against 1) spoofed device-id numbers, 2) the fact that the usual reason to factory-reset a phone is that the phone is going to be returned/sold to someone else)
Your solution (in only the case I have guessed) would be to acquire a "gaaps" package (yes, that's short for 'google apps') from a release date, platform appropriate to your device. (i.e. don't try to install the current lollipop apps on your GB device). This should include Google's sync and account settings background app and one-time-init (for initial set up upon purchase).
 If this sounds like your situation, just search for gapps or gaaps.zip.
 If this **doesn't** sound like your situation, just follow the advice above and provide more details. (did you just root/switch ROMs would also be relevant)
    good luck
    **-R**