Where do I add Refrigerant to a 2015 V60

Look for the low pressure port.

I have looked all over for the low pressure port. No luck. There is a port right up top that ties into a housing that also hosts both the low pressure AND high pressure lines. The port itself is sized for high pressure use and has a black cap with "6nM" on it. Every reason to believe it is for high pressure side discharge only. That said, if it's really the only port, is there a chance it's dual purpose and could feed the low pressure side?

If you have a gauge set try checking the pressure on the port. Then you will know what line it is.

Only have the gauge built into the top of the AC Pro can/hose. It won't seat on the top port as is. Volvo does have a schrader valve for the recharge port in their parts list, but it does not give any details or specs. Is it essentially an adapter? Don't know. I should also note that as of 2016 Volvo stopped providing any information about the location of a low pressure port. With my usual luck, it's a 2015.5 V60 and - based on diagrams I've found on the web - Volvo changed AC designs for 2016. If anyone can help...

Ask this question on some online Volvo Forums, you might find what your looking for.