Use the supplied PLA sample file for the first print. It avoids profile uncertainty and gives the printer a modest, known workload.
Clean the PEI sheet, align it on the magnetic bed and make sure the nozzle has no hardened plastic underneath. Run the stored leveling routine if setup was interrupted or the bed was disturbed.
Preheat for PLA and feed filament through the runout sensor into the direct-drive extruder. Extrude until the strand is smooth. Keep it away from the nozzle with tweezers after the head has stopped.
Start the sample and watch the skirt or first outline. Adjust Z offset in very small steps if the lines are separate or heavily ridged. Do not spin the four bed wheels during the print. They change the physical plane and invalidate the mesh you are trying to evaluate.
Leave the high-speed claims for later. A first print is about repeatable extrusion, a sound first layer and free motion. Listen for belt rubbing, cable contact and a rear fan shroud touching the bed’s path.
After the sheet cools, remove it and flex it. Inspect the model for an even base and aligned walls. Save a photo of the first layer along with the displayed Z offset and firmware version. Those details are valuable if a future update or nozzle change alters the result.
If the first sample did not go smoothly, it helps to work backward — assembly and cable routing are covered in the Neptune 4 Pro setup guide, while a stubborn first layer usually points back to the wheel and Z offset leveling sequence. The general first-print beginner checklist is also worth a look for habits that apply beyond this specific machine.