[HTC 10 ROMs, Kernels, Recoveries, & Other Developm] nkk71:
strange, seems you possibly have a different partition layout, can you please do the following adb commands:

adb shell
ls -l /dev/block/bootdevice/by-name

example:

C:\ADB\ADB_10>[B][COLOR="Blue"]adb shell[/COLOR][/B]
shell@htc_pmeuhl:/ $ [B][COLOR="Blue"]ls -l /dev/block/bootdevice/by-name[/COLOR][/B]
ls -l /dev/block/bootdevice/by-name
lrwxrwxrwx root root 1970-01-17 12:33 Linux -> /dev/block/mmcblk1p2
lrwxrwxrwx root root 1970-01-17 12:33 Microsoft -> /dev/block/mmcblk1p1
lrwxrwxrwx root root 1970-01-17 12:33 aboot -> /dev/block/mmcblk0p10
lrwxrwxrwx root root 1970-01-17 12:33 absolute -> /dev/block/mmcblk0p66
lrwxrwxrwx root root 1970-01-17 12:33 adsp -> /dev/block/mmcblk0p31
lrwxrwxrwx root root 1970-01-17 12:33 apdp -> /dev/block/mmcblk0p18
lrwxrwxrwx root root 1970-01-17 12:33 apppreload -> /dev/block/mmcblk0p64
lrwxrwxrwx root root 1970-01-17 12:33 board_info -> /dev/block/mmcblk0p1
lrwxrwxrwx root root 1970-01-17 12:33 boot -> /dev/block/mmcblk0p59
lrwxrwxrwx root root 1970-01-17 12:33 cache -> /dev/block/mmcblk0p61
lrwxrwxrwx root root 1970-01-17 12:33 carrier -> /dev/block/mmcblk0p53
lrwxrwxrwx root root 1970-01-17 12:33 cdt -> /dev/block/mmcblk0p23
lrwxrwxrwx root root 1970-01-17 12:33 cmnlib32 -> /dev/block/mmcblk0p16
lrwxrwxrwx root root 1970-01-17 12:33 cmnlib64 -> /dev/block/mmcblk0p17
lrwxrwxrwx root root 1970-01-17 12:33 cota -> /dev/block/mmcblk0p65
lrwxrwxrwx root root 1970-01-17 12:33 ddr -> /dev/block/mmcblk0p22
lrwxrwxrwx root root 1970-01-17 12:33 devcfg -> /dev/block/mmcblk0p14
lrwxrwxrwx root root 1970-01-17 12:33 devinfo -> /dev/block/mmcblk0p13
lrwxrwxrwx root root 1970-01-17 12:33 devlog -> /dev/block/mmcblk0p42
lrwxrwxrwx root root 1970-01-17 12:33 dip -> /dev/block/mmcblk0p35
lrwxrwxrwx root root 1970-01-17 12:33 dpo -> /dev/block/mmcblk0p20
lrwxrwxrwx root root 1970-01-17 12:33 dsp -> /dev/block/mmcblk0p57
lrwxrwxrwx root root 1970-01-17 12:33 extra -> /dev/block/mmcblk0p44
lrwxrwxrwx root root 1970-01-17 12:33 fataldevlog -> /dev/block/mmcblk0p41
lrwxrwxrwx root root 1970-01-17 12:33 fp -> /dev/block/mmcblk0p32
lrwxrwxrwx root root 1970-01-17 12:33 frp -> /dev/block/mmcblk0p50
lrwxrwxrwx root root 1970-01-17 12:33 fsc -> /dev/block/mmcblk0p45
lrwxrwxrwx root root 1970-01-17 12:33 fsg -> /dev/block/mmcblk0p29
lrwxrwxrwx root root 1970-01-17 12:33 hosd -> /dev/block/mmcblk0p11
lrwxrwxrwx root root 1970-01-17 12:33 hyp -> /dev/block/mmcblk0p9
lrwxrwxrwx root root 1970-01-17 12:33 keymaster -> /dev/block/mmcblk0p55
lrwxrwxrwx root root 1970-01-17 12:33 keystore -> /dev/block/mmcblk0p54
lrwxrwxrwx root root 1970-01-17 12:33 lksecapp -> /dev/block/mmcblk0p15
lrwxrwxrwx root root 1970-01-17 12:33 local -> /dev/block/mmcblk0p43
lrwxrwxrwx root root 1970-01-17 12:33 mdtp -> /dev/block/mmcblk0p34
lrwxrwxrwx root root 1970-01-17 12:33 mfg -> /dev/block/mmcblk0p2
lrwxrwxrwx root root 1970-01-17 12:33 misc -> /dev/block/mmcblk0p38
lrwxrwxrwx root root 1970-01-17 12:33 modemst1 -> /dev/block/mmcblk0p39
lrwxrwxrwx root root 1970-01-17 12:33 modemst2 -> /dev/block/mmcblk0p40
lrwxrwxrwx root root 1970-01-17 12:33 mota -> /dev/block/mmcblk0p56
lrwxrwxrwx root root 1970-01-17 12:33 msadp -> /dev/block/mmcblk0p19
lrwxrwxrwx root root 1970-01-17 12:33 persist -> /dev/block/mmcblk0p48
lrwxrwxrwx root root 1970-01-17 12:33 pg1fs -> /dev/block/mmcblk0p3
lrwxrwxrwx root root 1970-01-17 12:33 pg2fs -> /dev/block/mmcblk0p4
lrwxrwxrwx root root 1970-01-17 12:33 pmic -> /dev/block/mmcblk0p8
lrwxrwxrwx root root 1970-01-17 12:33 radio -> /dev/block/mmcblk0p30
lrwxrwxrwx root root 1970-01-17 12:33 ramdump -> /dev/block/mmcblk0p51
lrwxrwxrwx root root 1970-01-17 12:33 recovery -> /dev/block/mmcblk0p60
lrwxrwxrwx root root 1970-01-17 12:33 reserve1 -> /dev/block/mmcblk0p37
lrwxrwxrwx root root 1970-01-17 12:33 reserve2 -> /dev/block/mmcblk0p58
lrwxrwxrwx root root 1970-01-17 12:33 rfg_0 -> /dev/block/mmcblk0p24
lrwxrwxrwx root root 1970-01-17 12:33 rfg_1 -> /dev/block/mmcblk0p25
lrwxrwxrwx root root 1970-01-17 12:33 rfg_2 -> /dev/block/mmcblk0p26
lrwxrwxrwx root root 1970-01-17 12:33 rfg_3 -> /dev/block/mmcblk0p27
lrwxrwxrwx root root 1970-01-17 12:33 rfg_4 -> /dev/block/mmcblk0p28
lrwxrwxrwx root root 1970-01-17 12:33 rfg_8 -> /dev/block/mmcblk0p46
lrwxrwxrwx root root 1970-01-17 12:33 rpm -> /dev/block/mmcblk0p7
lrwxrwxrwx root root 1970-01-17 12:33 sec -> /dev/block/mmcblk0p49
lrwxrwxrwx root root 1970-01-17 12:33 skylink -> /dev/block/mmcblk0p52
lrwxrwxrwx root root 1970-01-17 12:33 slpi -> /dev/block/mmcblk0p33
lrwxrwxrwx root root 1970-01-17 12:33 sp1 -> /dev/block/mmcblk0p21
lrwxrwxrwx root root 1970-01-17 12:33 ssd -> /dev/block/mmcblk0p47
lrwxrwxrwx root root 1970-01-17 12:33 system -> /dev/block/mmcblk0p62
lrwxrwxrwx root root 1970-01-17 12:33 tool_diag -> /dev/block/mmcblk0p12
lrwxrwxrwx root root 1970-01-17 12:33 tz -> /dev/block/mmcblk0p6
lrwxrwxrwx root root 1970-01-17 12:33 userdata -> /dev/block/mmcblk0p63
lrwxrwxrwx root root 1970-01-17 12:33 venus -> /dev/block/mmcblk0p36
lrwxrwxrwx root root 1970-01-17 12:33 xbl -> /dev/block/mmcblk0p5
shell@htc_pmeuhl:/ $

Did the multirom boot menu ever show up for you? If not, please do the same as mentioned above.

As mentioned in the FAQs (guess you missed it ;))

What do the ROMs share?

All ROMs are separate, except /sdcard, which is shared between all Android ROMs.​

Glad to hear it :good:

No idea, please post a recovery.log after you flashed 2016-09-18.