On the 22nd of June Google changed its policy for Google Maps. New sites that have been created after the 22nd of June seem to be exhibiting some problems with a grey box where the map should be.
I have seen this with the Modern Tribe Events Calendar on one site which was simply moved from a development location to a live URL. It stopped working. Everything else was fine.
Up until June anyone could add a map to a site without having to set up an account with Google and an API key. The API key is associated with the website address. From the 22nd of June it appears that everyone needs an API key for all new sites in order to get map calls to work.
There is a fix available which I have used on one site and this fixed the problem.
Go to here: https://wpgeodirectory.com/this-page-didnt-load-google-maps-correctly-see-the-javascript-console-for-technical-details/ This site explains what has happened and contains instructions on setting up a key for your website and how to install and add it in.
I expect there will be many other workarounds shortly.
If your maps disappear at all, let me know please through the contact us page.