I think this may be a problem wich some Old QHY cameras may not work when the program tries to open and use more than once
And solved after SDK 21.7.16 url]https://www.qhyccd.com/html/prepub/log_en.html#!log_en.md[/url
Please download 21.08.03 (there are some other bug fixes with Linux),  and install   [www.qhyccd.com/html/prepub/log_en.html#!...Library_Installation]
Then check which version is selected

# check current SDK version
ls -al /usr/local/lib/libqhy*

ldd /usr/bin/indi_qhy_ccd |grep libqhy*

If use lsusb, you should see this:
1. plug the camera, there should be a 1618:c600

2. then the rules file works, it change to 1618:C601

3. now you should be able to connect to the camera, use any software, make sure the SDK version greater than 21.1.1

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 just to be clear, you mean you can not connect to the camera with INDI, and you see a reset after plug the camera?

If use lsusb, you should see this:
1. plug the camera, there should be a 1618:c600
downloadex?ri=%2Falimail%2FinternalLinks%2FrefreshToken&o=1&et=normal&ext=png&e=my%40qhyccd.com&f=8f5512e2-4ee5-452d-87e5-0979b53d9587&m=1_0%3ADzzzzyT1lK8%24---.KiXMsX60&n=temp4cj.png
2. then the  rules file works,  it change to 1618:C601
downloadex?ri=%2Falimail%2FinternalLinks%2FrefreshToken&o=1&et=normal&ext=png&e=my%40qhyccd.com&f=7a125d7d-ad2f-4534-8c2b-629a38c31c95&m=1_0%3ADzzzzyT1lK8%24---.KiXMsX60&n=temp4cj.png
3. now you should be able to connect to the camera, use any software, make sure the SDK version is greater than 21.1.1
check SDK version 

ls -al /usr/local/lib/libqhy*