Error through router : Template init / variable service failed

Hi,
I use my Grafana solution on a computer I can access through my network, or a router Ewon.
Everything is fine when I connect directly to the computer, but not through the router.

When I refresh my dashboards I get these errors :
Error 1 appears sometime on load : "Templating init failed
NetworkError when attempting to fetch resource."
Error 2 appears at each automatic refresh : "Template variable service failed
NetworkError when attempting to fetch resource."

Also on somes panels (random at each refresh / F5) I have the error :
Error 3 appears randomly on panels on load : NetworkError when attempting to fetch resource.

Looking in my browser console I see :
TypeError: NetworkError when attempting to fetch resource. initDashboard.ts:197:14
Using strings as events is deprecated and will be removed in a future version. (template-variable-value-updated) 26 emitter.ts:44:14
Uncaught (in promise) TypeError: NetworkError when attempting to fetch resource.
Uncaught (in promise) TypeError: NetworkError when attempting to fetch resource.
Uncaught (in promise) TypeError: NetworkError when attempting to fetch resource

Every time the popup with error 2 I see in my console :
Uncaught (in promise) TypeError: NetworkError when attempting to fetch resource

In the next picture you can see our ports in the router, 192.168.254.2 is our computer.
the port 4567 is to access to Grafana.
I think we did allow all necessary ports in the router (May be there is a websocket or else we did not identify ?) :


so I have no idea what’s happening here…

I’ve seen many error with a title close to mine where it is asked to check the DataBase so :

If someone can help me on this, Thanks in advance

I recommend turning on debug logging to gather more information about what Grafana is doing.

There are several other tools described in the Troubleshooting docs that might help as well.