Oh wow yikes. Alright did you buy it off aliexpress? Was it the jennyprinter or the sanjiu? I suppose if the z stop isn't working then the bed won't come up so that could be part of your issue but it's hard to believe you got three bad endstops. It makes me feel like it's a board issue or something. I thought I had an issue with my endstops during the build but realized it was due to a grub screw being loose on the short belt pulley. So I would first check all those just to be sure I guess. Have you tried to manually activate the end stops yourself?