can't create /jffs/

Hello, first time user of Merlin, ASUS RT-N66U H/W Ver B1 running RT-AC66U_380.65_4 OK Noted download site says to use 66U for B1 however the hardware disagree's and wont take it Enable JFFS custom scripts and configs and SSH ETC, reboot Formatted USB 2.0 device EXT 2. Tried 3 of such devices...