With some help from my mate and this thread:
https://forum.duet3d.com/topic/1595/quick-fire-question-change-wifi-network-ap-router
...it is up and running again.

Thanks for the support.
Mark

If I go the other route and upgrade from 1.18 to the current version, were there any significant changes which will need to modified in my printer set up?

Thanks for you prompt response, and for correcting my error in the header.

So if I understand that correctly, I need to go into the new WiFi access points setup and connect to the Duet, rather than use the Duet to connect to the axis point?
Mark

@rotarysmp Sorry, that header should read M587. If an Admin could ammend it, I appreciate that.
Mark

Hi All,

I have a working printer. A Mendel90 derivative a good friend designed. He did the original Duet Wifi set up. I just replaced my WiFi router, so I need to reconnect to the new router.

I tried the instructions on:
https://duet3d.dozuki.com/Guide/1.)+Getting+Connected+to+your+Duet/7

I am at an older version 1.18.1, but since it was working before, don't want to add variables by upgrading.

In YAT I get...

M115
FIRMWARE_NAME: RepRapFirmware for Duet WiFi FIRMWARE_VERSION: 1.18.1 ELECTRONICS: Duet WiFi 1.0 FIRMWARE_DATE: 2017-04-09<LF>ok<LF>DuetWiFiServer version 1.03 (ch fork)<LF>Flash size 4194304, free RAM 34296 bytes, WiFi Vcc 3.07V, host name: duetwifi, reset reason: Turned on by main processor<LF>WiFi is running as an access point with name DuetWiFi<LF>
M552
Network is enabled, configured IP address: 192.168.1.10, actual IP address: 0.0.0.0<LF>ok<LF>
M552 S0
WiFi server stopped<LF>ok<LF>
M587 S" removed from this thread " P"removed from this thread"
unsupported command: M587 S"xxxxxxx" P"xxxxxxxxxx"<LF>ok<LF>

I then tried the Macro method from here:
https://www.instructables.com/id/Duet-WiFi-Activate-and-Connect-the-WiFi-When-It-Do/

M552 S0<br>G4 P10000
M587 S"xxxxxxx" P"xxxxxxxxxx"

The instructions in the link above say to start the WiFi with M552 S0. I thought that ends it?
Anyway, I pulled the USB plug, replugged it and restarted YAT and have...
M552
Network is enabled, configured IP address: 192.168.1.10, actual IP address: 0.0.0.0<LF>ok<LF>

I get:
M98 P/macros/SetNetwork
Dud IP address: M552 S0<br>G4 P10000<LF>WiFi server stopped<LF>unsupported command: M587 S"xxxxxxxx" P"xxxxxxxx"<LF>ok<LF>

Checking the G-Code list, that M552 P100000 seems weird, so I tried replacing it with P0.0.0.0.

Now when I call the Set network macro, it doesn't error out on the first line, but I get the same "unsupported command" error on the second line.
M98 P/macros/SetNetwork
unsupported command: M587 S"xxxxxxxxxx" P"xxxxxxxxxxx"<LF>ok<LF>

I searched the web, but only found one link to this behaviour, but that thread drifted off into a Z homing issue.

I would appreciate your help in getting this reconnected and running again.
Mark