If you have experienced the Problem: Starting ArcGIS pro Returns a System Clock Error after Upgrading to ArcGIS pro 3. the following is a solution that may work and may not require contacting Esri support.
We have ArcGIS Pro 3.3.1 installed on a windows virtual machine with a Single Use license. The system clock error appeared after having to revert our machine using a snapshot after a windows update failure. Prior to reverting, the Pro install and licensing worked. It was not caused by upgrading, in contrast to the post above. After reverting to an earlier VM snapshot the clock error appeared ("The system clock is incorrect. Please set your clock to the current date and time."). In addition we could not Authorize ("All requested features have already been authorized on this machine") or Deauthorize ("There are no Single Use licenses to deauthorize on this machine") the licensing. Setting the clock did not clear the error. A full uninstall and reinstall did not clear the error.
Esri support helped fix this but nothing needed to be done by support staff. As the post indicates there is an issue in FlexNet. To fix, we canceled our existing Single use license and created a new Single use license; deleted the C:\Program Files\FlexNet folder; opened Add/Remove Programs and ran a Repair on ArcGIS Pro. After the repair the clock error disappeared and we were able to use the new Single use license to authorize the software.
