As well as SGP logs logs from the Celestron ASCOM driver are absolutely essential.
What I think is happening is that, because you are using a StarSense HC, pier flips before the meridian are not allowed. The StarSense HC doesn't have the full functionality of the NexStar HC and setting the side of pier is one of the things that can't be fully implemented.
Set SideOfPier() should work but only after the mount has crossed the meridian. If it hasn't then the error message that's shown in the SGP log is shown.
A driver log will show exactly what is happening, it is absolutely essential that you collect and send one that covers one of these failed flips.
Chris R