That could be if you have another USB/serial device that is responding to initial Gemini commands. When ASCOM driver searches for the correct COM port, it'll try each one in turn. If one of them responds to Gemini "hello" command, the driver assumes it's Gemini. You may want to make sure you use the correct serial port Gemini is connected to, select that COM port in the driver setup, and turn off Auto-Detect Gemini option:
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Paul Kanevsky