@dc42 Thank you

I just did it and everything looks to work , even the modem connecting again.
I still don't understand what kind of mistake and how many I did, I'm new in this field and I must admit that for me is much more complicated than I thought.
Thankyou !

I understand, but i found config (1), config (2) etc files..
I think that at this point I will look for a procedure to clean and reload firmware .
Hope it will not be so difficult..
Thankyou

I checked the SD card and I found several config .g files , I think that trying to update the software i did a mess !
However the M552 S1 command was present in all of them . I deleted the other config files thinking that they could conflict leaving only one of them, but the problem is still there. At this point I ask you if I can clean the SD card, reset everything and reload drives and updates from the beginning...

Hello everyone,

After some attempts to update the firmware of my Duet WIFI I managed to install version 3.0 (it was 2.02).
The card connects to WIFI only through the USB connection with the M552 S1 command on YAT. From here I can launch DWC and everything seems to be working. The problem arises when I close YAT disconnecting the USB cable to connect via Browser.
When the board is turned on, the Blue LED does not flash and always remains off, consequently DWC cannot connect.
I attach some photos hoping they will be useful to understand the problem
Thanks in advance for any help.
This is the screenshot of DWC connected with USB Cable and YAT with WIFI activated via M552 S1

This is the card connected with USB and YAT

Thankyou

@PuterPro
Yes I have two Z motors running in parallel connected to ZA and ZB slots on the DuetWIFI.
I'll change settings as you suggest, changing the Z4000 to Z 400.
Thankyou!

@Phaedrux
Thanks for the formula, I had been looking for it for a long time ...

@PuterPro

thank you
in fact I had many doubts about how to insert the Cofig file on the forum, now I know.
in a week I will finally be home and I will put all your suggestions into practice hoping to be successful.

Goodmorning everyone

I'm still far away from the printer for work reason, but I have my laptop and I elaborated the configuration file, same as I did at home and loaded on the DWC , processed by the RepRap cartesian configuration tool. Compared to the default data available on configurator I have entered only the essential data omitting changes about the dynamics of the axes (also because I don't know exactly which data to put for lead screw axes ) to have a file that for the moment allows me to homing and make the machine move correctly.
Instead of the Zprobe, I temporarily installed an NC limit switch which trigger at about 2 mm from the heated plate.
I have available and connected to the Duet two limit switches for every axe ( I think i have to choose one as the option on configurator is"low or high end"..) and they are NC .
Heated Bed is 310 x 310 , but the axes have a stroke of about : X 410, Y 410 and Z 290.
Attached all the config files,
Thank You.
tpre0.g tpost0.g tfree0.g stop.g sleep.g resume.g pause.g homez.g homey.g homex.g homeall.g config.json config.g bed.g

; Configuration file for Duet WiFi (firmware version 2.03)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v2.1.8 on Tue May 05 2020 07:43:24 GMT+0200 (Central European Summer Time)

; General preferences
G90 ; send absolute coordinates...
M83 ; ...but relative extruder moves
M550 P"My Printer" ; set printer name

; Network
M552 S1 ; enable network
M586 P0 S1 ; enable HTTP
M586 P1 S0 ; disable FTP
M586 P2 S0 ; disable Telnet

; Drives
M569 P0 S1 ; physical drive 0 goes forwards
M569 P1 S1 ; physical drive 1 goes forwards
M569 P2 S1 ; physical drive 2 goes forwards
M569 P3 S1 ; physical drive 3 goes forwards
M584 X0 Y1 Z2 E3 ; set drive mapping
M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z4000.00 E420.00 ; set steps per mm
M566 X900.00 Y900.00 Z12.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z180.00 E1200.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z20.00 E250.00 ; set accelerations (mm/s^2)
M906 X800 Y800 Z800 E800 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

; Axis Limits
M208 X-10 Y-10 Z0 S1 ; set axis minima
M208 X320 Y320 Z280 S0 ; set axis maxima

; Endstops
M574 X2 Y2 S1 ; set active high endstops
M574 Z1 S2 ; set endstops controlled by probe

; Z-Probe
M558 P5 H5 F120 T6000 ; set Z probe type to switch and the dive height + speeds
G31 P500 X0 Y0 Z2.5 ; set Z probe trigger value, offset and trigger height
M557 X5:215 Y5:195 S20 ; define mesh grid

; Heaters
M140 H-1 ; disable heated bed
M305 P1 T100000 B4138 R4700 ; set thermistor + ADC parameters for heater 1
M143 H1 S280 ; set temperature limit for heater 1 to 280C

; Fans
M106 P0 S0 I0 F500 H-1 ; set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
M106 P1 S1 I0 F500 H1 T45 ; set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on

; Tools
M563 P0 D0 H1 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined

@Phaedrux
Thank you so much for your kind help. I touched the motors after a second attempt to run a Home all axes and they were quite hot. But maybe was only impression I don't know.
I'm living for work tomorrow morning, far from home (and my printer ) for about a week. As soon I'll be back home I'll send you my Config file as come out from rep rap configurato for custom cartesian. In the meantime I'll study about your advices.
I'm so happy to know that somebody helping me.