We use Flexi 7.5 (and Flexi Designer 8.5)
Assuming 8.1 is similar to 7.5, you simply need to "Clear Preferences" .
This feature is listed on the Windows Start Menu.
It would be a desirable to back up your Swatch Table (in the Programs file system under Flexi or SAI) before clearing your preferences because Clearing Preferences is likely to send your Swatch Table back to the default setting. (I haven't verified this, but am told this will happen.)
Run Clear Preferences. You will then have to select your printer/cutter from the menu. Also you may see a blank menu in the Production Manager for a few seconds. Either wait or close/open the Production Manager.
And that is all there is to it!
I am reasonably sure this will fix your problem!