The site is experiencing technical difficulties.

Dear Gary Kovar, I tried to use WP_Places plugin, but I cannot add Google API key due to missing Save button and below the Google API key field are next message visible: “The site is experiencing technical difficulties. Please check your site admin email inbox for instructions.” I didn’t receive any emails within instructions. I deactivated all plugins with same result. I tried it at another Multisite WP installation with same result.
Is this plugin compatible to Multisite WP installations? How could I get used the plugin?
Thank You in advance sonarnew