1st try Restore Defaults under the Setup tab ...
If that doesn't help ...:
Go under the Views tab and make the "Accessories test" view "Visible" ...
Then exit out of the "Menu" system and cycle thru the views until the "Accessories Test" view is showing ...
If the GPS is intermittently showing "Not Connected", it's most likely the internal GPS is failing ...
You can connect an external GPS antenna and override the internal GPS ...
Rickie