Hi Josh,
Usually when ARP is not resolved for an IP, we see this error. Any number of reasons can cause this - including bugs, network issues, etc. We would need to know the full picture before a cause can be deduced. What is the version of code run...
I suspect we'd see some logs related to port 49. Either way, when you try to build the alternate stack, if you still run into issues, you can open a case with GTAC for assistance.