If you cannot calibrate the PX940V’s verifier, try this.
Most times this failure is due to dirt on the glass over the verifier, often not visible. To confirm this is the issue, print a test label and connect to the printer’s web page and look at the verifier’s image under Verification, Verifier Image. You’ll probably see something like this:
The vertical black lines aren’t on the label, it’s dirt on the verifier glass.
Open the front verifer arm.
Clean the glass with isopropyl alcohol and Q-Tips, or an alcohol wipe. Repeat until there are no lines on the verifier image, then try to calibrate the verifier again.
Note the row of label sensors next to the verifier.