Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
What map files will work on a Garmin device, depends upon (among some other things)
- their source
- their file-type and thus compatibility with the Garmin (in this case) Zumo 550
- whether they are regularly purchased and registered for usage (see 'their source' above, also.)
- whether the device's memory is full
- whether the device's firmware is corrupted or out of order or the device is not functioning properly and fully otherwise owing to any number of faults in the device.
Let me know which of these problems might be the cause, and also tell me what the whole problem *is*, and I will advise you further as appropriate.
(If the firmware is corrupted or might be, then the device's firmware should be updated through Garmin Express, or similarly directly from Garmin without intermediary or substitution... and a computer to do the updating might well be necessary.)