Run 1 sheet , wipe the sheet with a clean dry cloth, if you do not see a smear the coating is cured.

If the coating smears, power down machine clean UV lamp with alcohol and clean reflector that surrounds lamp so that reflector has a mirror like finish.
If the issue is not resolved replace UV lamp.

Run multiple sheets, remove a sheet from the middle of pile. Wipe sheet with a clean dry cloth if you see the coating smear it could have come from the back of the sheet that was on top of it in the pile. Check the back of sheet. If there any evidence of coating ? If so adjust scrapper blade , clean impression roller, clean scrapper blade or replace scrapper blade.