Assuming you don't have transmitters other than ISS and maybe a separate wind transmitter then see if you can still source a 6351 Vue console from somewhere and use that with pressure setting = Altimeter in place of the Envoy. (If the pressure error is important enough to you!)

By what means are you configuring the Envoy barometric pressure in relation to Station Elevation & Sea-Level reading?

.......
"when you say it disconnects from the sensors, does this mean mean that WS View Plus (WSV+) stops displaying the live data ? : no
(if no sensor data are transmitted, WSV+ disconnects respectively doesn't build up the connection to the gateway)
If so, does the WebUI (https://IP-address-of-your-GW1100) show the same behaviour ?" : yes

So - when you say here "no", that means that WSV+ still DOES display data => the GW1100 receives sensor data (otherwise WSV+ couldn't display them) - so it doesn't disconnect from the sensors.

Before I go to further conclusions, please confirm that WSV+ displays the live data (or you said "no" = doesn't stop, but meant "yes", it stopped = does no longer display data).

To make it simple: can you see live data of the GW1100 via WS Vew Plus ?

Waiting for your reply and will take it from there.

'm sorry I wasn't precise when describing the problems with my GW1100;

"when you say it disconnects from the sensors, does this mean mean that WS View Plus (WSV+) stops displaying the live data ? : no
(if no sensor data are transmitted, WSV+ disconnects respectively doesn't build up the connection to the gateway)
If so, does the WebUI (https://IP-address-of-your-GW1100) show the same behaviour ?" : yes

Reconnect within 5 seconds doesn't work technically - so what do you mean ? : no
- you restart WS View Plus after five seconds ? : no
- you make a reset (pressing the black button between the red and blue LEDs for > 5 seconds) ? : yes

I assume that your GW1100 is connected via WiFi/router/internet to ecowitt.net - so, do the one-minute updates also stop ? : yes
Are there gaps in the table view of your ecowitt.net dashboard ? (5-minute records). : yes

How do you know that the GW1100 disconnects from the sensors every two days ? :  disconnection dates :22/03/24, 25/03/24, 30/03/24, 02/04/24, 03/04/24,04/04/24, 09/04/24,12/04/24.
Are you permanently sitting in front of the WSV+ app ? : no
What indicates for you the 2-day disconnect ? : it's approximate
Does this disconnect always happen at the same time (clock) or after the same period of time (duration since last reset/restart) ? : no, without my intervention the gw1100 no longer receives sensor data.

I should add that my HP2550 console receives sensor data without interruption.

I hope I've described my problem accurately.
thank you for your patience

Good evening

I think its a http v.s. https issue.  Your sticker image at http://weatherelement.com/Candler/Sticker.jpg is HTTP only.  I tried using https, but it fails to http.  Modern browsers prevent loading mixed (http) contents in a https page.

Contact the admin for weatherelement.com and ask them to add a LetsEncrypt cert to allow the content to be served via https.