DIAGNOSIS Yep, that's almost certainly clogged printhead nozzles. Ink dries out in the tiny jets if the printer sits unused for a while, even with cartridges that are half full.
FIX You need to run the printer's built-in cleaning utility. 1) Open the HP Smart app on your phone or computer. 2) Select your printer, then go to 'Printer Settings' or 'Tools'. 3) Look for 'Printer Maintenance' and select 'Clean Printheads'. Follow the prompts. This will use a bit of ink to flush the nozzles. After it's done, print the 'Print Quality Diagnostic Report' from the same menu to check your work. Repeat the cleaning cycle once if it's still bad, but no more than twice in a row.
IF THAT DIDN'T WORK If software cleaning fails, you can try a manual clean. Dampen a folded paper towel with distilled water (not tap water). Place it at the bottom of the service station on the right side of the printer. Use the printer's menu to move the printhead to the center for access, then gently dab the printhead nozzles (the copper-colored strip) onto the damp towel for 30 seconds. Do not rub. Run a cleaning cycle afterwards.
HEADS UP Avoid cheap, third-party 'compatible' ink cartridges with this model. They often have inconsistent ink formulas that clog much faster than HP's own cartridges, leading to this exact problem.