It is likely that the Printhead has gotten dirty.
(1) Turn off Label Printer and allow it to cool down.
(2) Open the Cover and use the provided alcohol pads to clean the Printhead and Platen Roller. (Any 70% Alcohol pad would work;These are commonly available in pharmacies and grocery stores as well as on Amazon.)
(3) Allow 2-3 minutes for components to dry, then close the Cover and turn Label Printer back on.
NOTE: Firmly press the Cover to confirm that it has been completely closed.
If the issue persists, please also try to print the attached sample label to ensure the cause is not from the source file.
Finally, it is possible that something has interfered with Phomemo PM-246's driver. Please uninstall Phomemo PM-246, restart your computer, and install the newest Phomemo PM-246 driver available on https://phomemo.com/pages/download-for-phomemo-4-6-label-printer