MConnect can't find Pi when using wifi

I just installed Volumio onto a Raspberry Pi 2b. Unfortunately, while I like the look and feel of Volumio, I cannot see or control the Pi with my MConnect phone app when using wifi. Interestingly enough, I am able to control the Pi on my PC while on wifi. I am also able to see and control the Pi with my phone app when using the ethernet. Please let me know what I need to do to get the Pi to appear and work on my phone app while using wifi. I’m a newbie to raspberry pi’s and network audio so I ask for your patience.