Why is my LG70 saying I need Google Play Services to open my Gmail?

[snailing1]

All of a sudden (to me!) I am getting this msg when attempting to open Gmail :

"Gmail won't run without Google Play Services, which are missing from your phone."

When I then tap "Install Play Services", the screen goes white and stays there.

NB: Phone is nearly out of storage.

I *can* still use Maps, Chrome & Google search; however, search is telling me I can't use Google Now cards until Play Services is reinstalled.

Thanks for any insight!

Clueless in No. Virginia