Wife's iPhone can't connect to our VOIPO home number

I've had VOIPO for a year and love it. The wife and I just switched our cell service to T-Mobile and got new phones. I have Android (Samsung Blaze) and she has an iPhone 4. The trouble is that my wife cannot connect to the home VOIPO number from her iPhone. When she calls, the home phone rings and I pick up. She can hear me, but I can't hear her. Her phone behaves this way for 20 seconds, then says "call ended". I also noticed that her iPhone continues to display "calling home" even after I've picked up. With a good connection, the iPhone should display the name of the contact ("home", in this case) with call duration underneath. That doesn't happen. So its as if the home phone has connected to the iPhone, but the iPhone hasn't connected to the home phone. Weird. I have no problems either way with my Android (edit - Android phone is having similar problems). The summary is:

iPhone to Voipo - Voipo seems to connect, iphone seems not to connect. iPhone hears the Voipo phone. Voipo phone cannot hear iPhone.
Voipo to iPhone - no problem at all
Android to Voipo - no problem (edit - Android hears Voipo phone. Voipo phone cannot hear Android)
Voipo to Android - no problem

Anyone seen this before?

It sounds like a T-mobile - iPhone 4 problem. Tmobile does not support iPhone4 in all areas. We have 2 iPhone 5 and one iPhone 4S on tmobile network and the 4S does not have proper data connection. Though t-mobile support iPhones, but officially they do support iPhone 5 only. In very few markets they do have iPhone4 and 4S compatibility. It depends on where you live. I live in San Jose, CA and they do not support 4 and 4S officially here, but 5 is fully supported. Is your wife able call all other numbers without any issue from her iPhone 4?

New info. I tried to call home today from my Android and experienced similar problems. I edited my original post. At first, it seemed the VOIPO phone and Android were operating flawlessly, so I suspected an iPhone problem. Now, it seems that the cell phones are working, but that the VOIPO phone has problems.

One-way audio is typically a sign that your router's firewall is blocking traffic. My suggestion would be to open up a support ticket with Voipo. Make sure you give them all the call reference logs for these failed calls by going to vPanel's Call History and clicking on each call. I'm confident they can figure out the source of the issue.

I had issues like that with ANY incoming call until I dealt with my router. I was able to specify a DMZ to my Grandstream device which opens ALL ports to the outside. It's virtually the same as not having a router at all to the modem. That solved all of my probems. It's been working great since.