Josh G wrote in post #18607974
I recently bought a Sony A7iii and a Godox V8600II-S Flash. The on-camera V860II works great as a master with my slave My Godox AD200 units, but I can't get my Godox AD360II-C strobe to work with the V860II as a slave unit in TTL mode. It will work in manual mode though.
What's the firmware version on the AD360II-C (it's at the top of the C.Fn menu)? The AD360II-C predates the -S triggers, and must be at v2.6 or later (current version is 2.8) to be compatible with the -S triggers, and v2.7 to be compatible with the -F/-O triggers. v2.6 was released in April 2016.
I was under the impression that all 2.4ghz Godox flashes could fully communicate with each other regardless of their camera designation (canon, nikon, sony, etc..) Am I mistaken?
Well, the X1R receivers and the TT350 are not supposed to be able to do cross-brand TTL, but all the other TTL-capable lights should be able to be used the way you describe. That's the way it's supposed to work: remote power control, HSS with any of the Godox lights and TTL with any of the lights that are capable of TTL.
Whether it actually works that way can be a bit different. 
I'm having some seriously rotten luck with HSS/TTL and my TT685C from my GX-7 and XProO, and some rotten luck with HSS with my TT600 speedlights and my XPro-F, but that's another story.
Do I need an X1R-S receiver on the AD360II-C to make it work in TTL with the V860II-S? Or do I need a X1T-C Transmitter on the A7iii body?
No. You shouldn't need any of that and the hotshoe contacts wouldn't match the foot pins, and the gear would be manual-only (although with the MI hotshoe, it might not even work to sync). The built-in transceivers in the Godox speedlights and AD360II should be able to autoswitch between the five supported systems even in the same shoot.
