on Nikon, Fuji, Sigma, Sony, Olympus and Panasonic cameras, the only flashes you can use for cross-TTL are Canon, Nikon, Sigma, Fuji, Olympus and Panasonic system flashes and not all flashes are compatible but you may be able to create a custom profile for your flash via your computer (can store up to 10 custom flash profiles)
on Canon cameras, the only flashes that will work in remote TTL mode are Canon system flashes
on Pentax cameras the only flashes that will work in remote TTL mode are Pentax system flashes
there is a different Cactus V6II model for Sony Cameras and Sony mount flashes but you can use your Canon or Olympus flash on a standard version and triggered by a Sony a7 with a Sony version trigger.
After setting the V6 II to auto-detect (AUTO) from a manually selection camera system, you must restart the V6 II for the selection to take effect.
HSS only works to 1/4000th sec on Panasonic GX85 cameras due to timing differences
you may need to remove the hotshoe spring plate on some Olympus E-M1 cameras to ensure good contact, and then you must mount the v6ii and with camera turned on, must press the shutter halfway before turning it on into tx mode .
How to make the E-M1 compatible with a Cactus V6 II - note that I do not have a problem with my E-M1 Mark I or E-M1 mark II
the locking pin is optimised for Canikon so the locking pin may not lock on Olympus cameras or Olympus flashes (can try pulling the flash back 0.5mm)