No longer centering, window pops up then disappears

My SGP has stopped centering. It can slew, but when I click on “center” a window briefly pops up then disappears. I can plate solve, sync and slew manually, but the centering function won’t operate. Any ideas what to check and how to restore?
SGP Windows 8.1

First, I would suggest you download the latest stable release (.23) and see if that fixes the issue.

Second, please see this thread on how to ask for help.