For more than a year now my GMC-320 plus is no longer counting. It comes on and the software works, but counts zero. It worked well for over a year after I bought it. Your advice will be highly appreciated.
Just throwing my thoughts out there. Perhaps the GM tube is broken, damaged? I have seen them on Ebay for ~$30 US. Might try contacting GQ Electronics directly support@gqelectronicsllc.com to see what they think.
Check the Tube voltage too. With 10M internal meter, it should read about 150V on 1000V range. With 2M internal meter, it should read about 35V on 1000V range.