Because you don't format data. But you lost all data if not backup. So i can say newest version of TWRP work not good. It encrypt internel storage that why we can't find normal data there. Wait to new TWRP version
Bro, i got same issue but i found the way to escape. Install new eu rom on twrp then bootloop to twrp , next go to install page and " format data" then reboot. You can go to new rom but lost all data. Remember do not input password for encrypt data again. Encrypt data make this issue