This is a density setting. In Printing Preferences > Options , reduce heat/density for dark print (smudges), increase for light print. Also, ensure you are using high-quality direct thermal paper (not thermal transfer ribbon).
: Setting up the "Virtual USB" port is a common hurdle. If the incorrect port is selected during the driver wizard, the printer will not respond even if the driver appears "successfully installed." Product Specifications & Performance pozone thermal printer pp610 driver download install
A. Typical Self-Test Procedure (generic): This is a density setting
Windows Update overwrote your driver. Fix: Reinstall the driver as per Part 3. Then disable automatic driver updates: reduce heat/density for dark print (smudges)