Ender 3 pro, many upgrades but CR touch still won't work

Depending on the cable you have, this sounds like the signal wire isn’t working correctly. It’s either the black & white two wire plug, or the end two pins on a 5 pin connector.

If marlin deploys the probe, then retracts and deploys it again, then errors - then it doesn’t see the level shift coming from the probe to indicate a state change.

In the BLTouch FAQ - this is shown as the G and OUT pins on the probe port.