Q: background map in maps app not visible

Are you connected to the internet? Are you connected via cellular or Wi-Fi? You need to have a data connection to see the map, so if you are on cellular and have cellular data turned off, or do not have Maps set to use cellular data, you will not see the map. Make sure you are connected to the internet. You can also try restarting your iPhone by turning it off and back on again to see if that fixes things.

RLaughy,

If an app you installed unexpectedly quits, stops responding, or won’t open - Apple Support

Although Maps is a preinstalled App, the first two steps of the linked article still apply.