Although we use one of the fastest and most reliable hosting services available, there was an incident recently which caused a loss of some data. We are still working with the provider to understand and avoid this issue in the future, but we have corrected the immediate problem.
Please go to Settings > Data Cache > Check for Updates to get the latest and complete maps data. Note this will cause a full download of all maps and other data needed for all cities, regions, countries, routes & tracks that you have marked with a green (or yellow) star. It is recommended you do this while on a WiFi connection.