Unknown error

While installing Facebook application on mobile it gives me an error which as follows:

Unknown error occurred while installing app - "504"

Details:
HTC M8
Android version 5.0.1 lollipop

I did try twice today so got any information please share.

Thanks

remove your google account by going to the settings for your device, then accounts and google. Hit remove account. Reboot your android and add the account once again.

Next, in the settings, go to apps (applications) and swipe to find ‘all’ of your apps. Scroll down to google services, then click clear data and finally force stop.

I shall try tomorrow see if it work (hope so).

Try searching this error code on google.... Google has fix for all their error codes