R9000 5ghz ssid visible, but can not be connected.

[GeneW]

It was working fine. last week the 5G wifi suddently has issue that cant be connected from any device, but the ssid visible.  2g Wifi is working fine.  Tried reset, factory restored, downgraded firmwares couple times, but no luck.  Any help will be appreciated. Thank you. 

Current firmward: V1.0.5.38 (latest)

I found the  debug page,  I have this report (5G wifi -negative temperature):

http://www.routerlogin.net/debug.htm

Basic Information
	CPU Load	CPU1: 4.47% CPU2: 4.7% CPU3: 3.81% CPU4: 4.57%
	Memory Usage(Used/Total)	134MB/1006MB
	Flash Usage(Used/Total)	158MB/512MB
	Network Session(Active/Total)	348/65536
	CPU Temperature	49
	2G WiFi Temperature	54
	5G WiFi Temperature	-174
	60G 11ad baseband temperature	66.582
	60G 11ad antenna array temperature	42.187
	System Uptime	01:13:16
	Wireless driver version	4.0.1756.382