Bad first layer and warping issue is the most common issue experienced by many beginners.
It can caused by:
1) Bed not leveled
If the first layer not printed consistent, some area thicker or some area thinner. Check bed leveling, make sure the bed is leveled properly.
Check out Bed Leveling Problem.
2) Greasy bed
If you experiencing the first layer adhesion problem, the part warp during printing process, fall off or stuck to the nozzle. Wipe the bed with rubbing alcohol or isopropyl to clean the oil or grease on the bed. They can be bought from local pharmacies.
3) Build platform temperature low
If the part warp during printing process. Check the filament printing guide, make the print setting is using the correct bed temperature to the material. If you set it correctly, but the bed just not heating up, check if the heated bed wire connection. Check the heated bed wire on the main board.
For CR10 Pro or CR10 Max, the newer version may come with the energy saver function, turn it off to make sure the bed is heated during the entire printing process.
4) Print setting issue
Check print setting, make sure first layer speed is slow and hot enough for the first layer to stick firmly on the bed. Turn off the part fan/cooling on the first layer, we suggest to start the part fan on 2nd or 3rd layer onwards.
5) Under extrusion
Check Under Extrusion
Share with us in the comment, what caused your bad first layer and how you solve it.