Hi there! I know this is so basic and I'm embarrassed to not understand what the issue is. I have a phottix indra 500 flash and a sony a7r2...because I'm new to sony and didn't want to buy more triggers and remotes, etc. I thought I would start with a long synch cord, which I have. I had to buy an adapter to make the cord I have work...so, I set it all up and NADA, nothing...what could the possible issues be? THANKS so much in advance!

A few possibilities exist, either wrong cord or wrong adapter.  The a7r2 has the Sony multi interface shoe...perhaps your cord or your adapter are for the old style Sony hot shoe?

Hi, thanks tinplater! So cords and hotshots are not universal? Crazy town.

Basic manual syncing shouldn't be a problem. I do it all the time with all sorts of hotch-potch gear. Maybe check the basic settings, manual on both camera and flash, shutter at 1/160 or less, exotic functions off. There are also wireless triggers that work for manual syncing irrespective of brand but if you buy a few sets of those, it's the same cost as a native flash with TTL, HSS etc. You could also check for second hand flashes for your Sony. They tend to have fairly low resale value. I've bought flashes at a fifth of the retail price, although that requires some patience.

Getting to basics... what is the flash setting on your camera. You should be able to find it in the menu. Try setting to Fill if not set to that already.