I would recommend closing any open applications in multitasking and restarting the device. If unfamiliar with multitasking, I have included a screenshot on how to process an application close. Test the results after processing these steps.
If the issue persists, see the section labeled Troubleshooting Maps in the article below.
Thanks for the suggestions Jason - I have already quit the app, restarted my iPhone and reset my iPhone, and checked the Using Maps page, all with the same result. What I need to be able to do is remove the app then download it again but of course this is impossible as it is part of the iOS. I don't want to wipe my iPhone unless it is really the only way to get a working map app again.