i was on open beta 21(7.1.1) on oneplus 3 , when i tried to install any rom of (6.0.1) ultimately i got black screen or bootloops, sometimes it shows that twrp didnt installed any rom, i tried everything imcluding changing roms and twrp and gapps and rom file, any idea what is wrong ?
Installed MM firmware? I think last was 3.2.8 check here flash the file in TWRP followed by rom, gapps etc..