It happened because your previous TWRP is installed in different place in your device than TWRP used in this rom. By flashing this rom you don´t remove earlier TWRP from your device but have two TWRP. So if you want to flash this rom you need to remove your earlier TWRP first.Not sure what caused it. I flashed the boot.img from the Ressurection Remix rom and then the twrp (3.2.1) i used there. Now I'm at least able to access recovery again and flash roms, but not sure how to get this one to work. So for this to work i should use a specific TWRP version or?