Hi 96902,
The problem is you're using the wrong firmware... the firmware you currently have installed in your G90 is for a non-GPS device.
If using the correct firmware you will have a red GPS icon if no antenna is detected or no GPS lock is available or a turquoise icon showing the strength of the GPS signal.
GPs and non-GPS G90's use entirely different firmwares.
You can use a non-GPS firmware in your GPS G90 (as you currently have), but you'll loose any GPS functionality.
Don't use G90 + GPS firmware version G90-A770_553-S-H as it's very buggy.
Use the older G90 + GPS firmware version trunk r439M which is much better and perfectly stable (lacks time-lapse function).
P.S. You did buy a G90 + GPS and not retrofitted a GPS antenna to a standard G90 as the internal hardware is different.
P.P.S. I contacted Doreen at SZDome requesting the latest firmware (when I bricked my G90) and heard nothing back :-(
Why can't they just make the firmware downloads available from their website?