I did try all three channels and did not see any change in behavior.
I have accessed it via duettest.local and it's ip address without seeing any difference. I have not done a wireshark trace.
After I posted yesterday, I was finally able to get a "stable" connection for a couple of hours - though I really have no idea why as I did not change anything. Turned it off for the night and came back this morning and I have the same issue. I bought the board from Filastruder so will contact them about the warranty and will reference this thread as you recommended. I was suspicious of the WiFi module but wanted to be certain I had not missed something.

Thanks for you input.

I have a new Duet WiFi board that does not want to stay connected. Typically, my connection lasts 8 seconds. Sometimes, I get the "Cannot establish a connection to the Duet Firmware," but usually it will connect.

I've gone through the troubleshooting guide and looked at numerous posts. The module connects to my router without issue. In fact, I really don't think it ever disconnects from the router as I can ping it without fail (even when Duet Web Control says the last HTTP request timed out or that it cannot establish a connection to the Duet Firmware). Ping times are usually in the 4-8 ms range but sometimes will be between 100-200 ms (no real pattern and it will usually reduce to the 4-8 ms range fairly quickly). About half the time when I ping the Duet, it will lose the first 1-3 packets before responding. I can only think of one occasion where it missed a packet after it started responding.

Here's the relevant part of M122 (via USB) (immediately following a disconnect):
=== Network ===
Slowest loop: 1.47ms; fastest: 0.01ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0) Telnet(0)
HTTP sessions: 0 of 8

• WiFi -
  Network state is running
  WiFi module is connected to access point
  Failed messages: pending 488, notready 0, noresp 0
  WiFi firmware version 1.21
  WiFi MAC address 5c:cf:7f:76:71:fb
  WiFi Vcc 3.35, reset reason Turned on by main processor
  WiFi flash size 4194304, free heap 17272
  WiFi IP address 192.168.1.22
  WiFi signal strength -51dBm, reconnections 0, sleep mode modem
  Socket states: 0 0 0 0 0 0 0 0

WiFi debugging output included with M122 after a disconnect:
WiFi: Conn 0: free
WiFi: Conn 1: free
WiFi: Conn 2: free
WiFi: Conn 3: free
WiFi: Conn 4: free
WiFi: Conn 5: free
WiFi: Conn 6: free
WiFi: Conn 7: free
WiFi:
WiFi: xmit: 0
WiFi: recv: 0
WiFi: fw: 0
WiFi: drop: 0
WiFi: chkerr: 0
WiFi: lenerr: 0
WiFi: memerr: 0
WiFi: rterr: 0
WiFi: proterr: 0
WiFi: opterr: 0
WiFi: err: 0
WiFi: cachehit: 0
WiFi:
WiFi: xmit: 2
WiFi: recv: 17
WiFi: fw: 0
WiFi: drop: 11
WiFi: chkerr: 0
WiFi: lenerr: 0
WiFi: memerr: 0
WiFi: rterr: 0
WiFi: proterr: 11
WiFi: opterr: 0
WiFi: err: 0
WiFi: cachehit: 13
WiFi:
WiFi: xmit: 37
WiFi: recv: 55
WiFi: fw: 0
WiFi: drop: 2
WiFi: chkerr: 0
WiFi: lenerr: 0
WiFi: memerr: 0
WiFi: rterr: 0
WiFi: proterr: 0
WiFi: opterr: 0
WiFi: err: 0
WiFi: cachehit: 0
WiFi:
WiFi: xmit: 15
WiFi: recv: 6
WiFi: drop: 0
WiFi: chkerr: 0
WiFi: lenerr: 0
WiFi: memerr: 0
WiFi: proterr: 0
WiFi: rx_v1: 0
WiFi: rx_group: 3
WiFi: rx_general: 3
WiFi: rx_report: 0
WiFi: tx_join: 4
WiFi: tx_leave: 2
WiFi: tx_report: 9
WiFi:
WiFi: xmit: 0
WiFi: recv: 0
WiFi: fw: 0
WiFi: drop: 0
WiFi: chkerr: 0
WiFi: lenerr: 0
WiFi: memerr: 0
WiFi: rterr: 0
WiFi: proterr: 0
WiFi: opterr: 0
WiFi: err: 0
WiFi: cachehit: 0
WiFi:
WiFi: xmit: 9
WiFi: recv: 37
WiFi: fw: 0
WiFi: drop: 0
WiFi: chkerr: 0
WiFi: lenerr: 0
WiFi: memerr: 0
WiFi: rterr: 0
WiFi: proterr: 0
WiFi: opterr: 0
WiFi: err: 0
WiFi: cachehit: 2
WiFi:
WiFi: xmit: 9
WiFi: recv: 10
WiFi: fw: 0
WiFi: drop: 0
WiFi: chkerr: 0
WiFi: lenerr: 0
WiFi: memerr: 0
WiFi: rterr: 0
WiFi: proterr: 0
WiFi: opterr: 0
WiFi: err: 0
WiFi: cachehit: 9
WiFi:
WiFi: avail: 4
WiFi: used: 4
WiFi: max: 4
WiFi: err: 0
WiFi:
WiFi: avail: 8
WiFi: used: 0
WiFi: max: 2
WiFi: err: 0
WiFi:
WiFi: avail: 4
WiFi: used: 1
WiFi: max: 1
WiFi: err: 0
WiFi:
WiFi: avail: 10
WiFi: used: 0
WiFi: max: 2
WiFi: err: 0
WiFi:
WiFi: avail: 10
WiFi: used: 0
WiFi: max: 0
WiFi: err: 0
WiFi:
WiFi: avail: 8
WiFi: used: 4
WiFi: max: 4
WiFi: err: 0
WiFi:
WiFi: avail: 8
WiFi: used: 5
WiFi: max: 6
WiFi: err: 0
WiFi:
WiFi: avail: 10
WiFi: used: 0

Signal strength is consistently between 45 and 52. I've tried moving closer and further from the router (Linksys WRT3200 ACM with stock firmware) with no change in behavior.

Ajax tries set anywhere from 1 to 10 without any noticeable change (8 second connections no matter the number of tries).

When I received the board, it had 1.21 firmware and WiFi firmware 1.21 rc4 on it. I went ahead and upgraded to 2.0 and 1.21 today (via fallback method) just in case it would make a difference - but it did not seem to change anything.

Since I have not had it stay connected for longer than a few minutes, I've not had a chance to print anything to know if the disconnects only occur at idle.