Interesting.
My truck has/had the same issue, but my findings were different....exactly the opposite actually. After reading this thread I went out and popped out the SD card, found the write protect tab already in the position away from the pins.
1. Found write lock tab in position away from pins
2. Slid tab down to be closer to pins, reinserted
3. Powered truck on, got the same message
4. Went to NAV, and hit ok on the warning message about initializing
5. Powered truck off
6. Powered truck back on, warning message did not display
7. Powered truck back off
8. Removed SD card and moved write lock tab to position farther away from pins, reinserted
9. Powered truck on, initially received a message stating that SD card had been removed, went away and GPS worked normally
10. Powered truck off and back on
11. GPS initialized with no error messages whatsoever
My goal here was to recreate the issue once I found what resolved it, which I was unable to do. It is almost as though you have to remove the card, move the write lock tab, and confirm the message on initialization and it doesn't matter which position the write lock tab resides. An odd one for sure.