iOS/iPhone/iPad must have location reporting enabled in MSB App, Safari, or Chrome (whichever you are using).
You must be set it to "While Using the App" or "Always" instead of "Never". Pick "Always" to never be prompted again.
To make this change, go to Settings>Privacy>Location Services and find either MSB, Safari Websites or Chrome.
Here is a screenshot of what that looks like:
If you have confirmed those settings are correct, this can also be caused by waypoints that have invalid Latitude and Longitude set. Go to the Waypoint edit screen and delete any that are invalid.