Tried tug a 3.1.1.2. It didn't help. But I found that, when I connect to laptop, it doesn't show internal memory even when I select file transfer. In twrp
recovery, when I connect to laptop, I can see memory in laptop.
Strange, did you reboot to recovery after formatting the partitions? I've not tested that.
I always flash using sideload in TWRP (advanced-sideload). Then you don't have to copy the files to the OPO first.
From terminal (Linux) or command prompt (Windows):
adb sideload rom.zip
adb sideload opengapps.zip
(ofcourse use the real filenames).