It sounds like you've already made several troubleshooting attempts. Here are a few additional suggestions to consider:
Check the first layer: Ensure your nozzle is at the correct height from the bed. The distance should allow for good adhesion but not be too close. Try adjusting the bed level or nozzle height to achieve the optimal first layer.
Improve bed adhesion: Clean the bed surface with isopropyl alcohol to remove any oils or residue. Consider using a bed adhesive like hairspray, glue stick, or a specialized 3D printing adhesive to improve adhesion.
Verify bed level: Confirm that your bed is properly leveled by checking the four corners and the center. Adjust the leveling knobs or springs as needed to achieve a flat and even bed.
Adjust first layer settings: In Cura, you can try adjusting the initial layer flow rate, initial layer speed, or initial layer height. Experiment with these settings to see if they have any positive impact on the print quality.
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