VXDIAG VCX FD Failed to Connect DoNET via 5GHz?

One of our customers was trying to connect VXDIAG VCX FD VCI via DoNET (5GHz) but failed. Photo attached:

VXDIAG DoNET 5G 1 VXDIAG DoNET 5G 2 VXDIAG DoNET 3

It should be noted that VXDIAG works with 2.4GHz DoNET remote connections and does not appear to recognize 5 GHz connections.

VXDIAG DoNET 2.4GHZ

He changed to another phone (2.4GHz) and it worked fine.