What Does This Error Mean?

Prusa print not sticking is almost always caused by a first layer that is too far from the bed, or a dirty or greasy bed surface. Clean the PEI sheet with isopropyl alcohol and re-run Live Adjust Z to lower the first layer until it squishes slightly.

Affected Models

Prusa MK4
Prusa MK3.9
Prusa MK3S+
Prusa MINI+
Prusa XL

Common Causes

First layer too far from bed — Live Adjust Z value not negative enough
PEI sheet contaminated with skin oils, hand cream, or dust
Bed temperature too low for the filament being printed
PEI sheet worn smooth in high-use areas — no longer provides adequate grip
Filament moisture causing poor layer bonding and warping at the base

How to Fix It

Clean the PEI sheet with isopropyl alcohol.

Apply 90%+ isopropyl alcohol to a clean paper towel and wipe the entire PEI sheet surface. Skin oils from touching the sheet are invisible but prevent adhesion entirely. Always handle the sheet by the edges only after cleaning.
Adjust Live Adjust Z to bring the nozzle closer to the bed.

During the first layer of a print, use the Live Adjust Z function on the Prusa LCD to lower the Z offset. The first layer should squish slightly into the PEI surface — a value between -0.5 and -1.5 is typical. If it looks like a round tube sitting on the surface, it is too far away.
Increase bed temperature for the filament type.

PLA needs the bed at 60°C, PETG needs 70–80°C, and ABS needs 100–110°C for reliable adhesion. In PrusaSlicer, the correct temperature is usually set automatically by the filament profile. If using a custom profile, verify the bed temperature is appropriate for your filament.
Try washing the PEI sheet with dish soap.

For stubborn residue that IPA cannot remove, wash the PEI sheet under warm water with a drop of dish soap, rinse thoroughly, and dry with a clean paper towel. Dish soap removes oils and wax-based residue that IPA leaves behind. After washing, wipe with IPA before the next print.
Replace a worn PEI sheet.

PEI spring steel sheets have a finite lifespan — the textured surface gradually wears smooth in heavily used areas (usually the center). A smooth PEI surface that has lost its texture will not grip any filament reliably. Prusa sells replacement spring steel sheets for all their printer models.

When to Call a Professional

Print adhesion is a calibration and maintenance issue — no hardware repair is needed. A worn PEI sheet is a replaceable consumable available directly from Prusa Research.