Android app doesn't display the connection

I installed openHab on my Synology NAS via Docker.
When I launch the app on my Android smartphone, I have an error : “no network connection available” whilst it display connected inside the parameters.
Do I have to open specifics port on my NAS or pages in openHab ?

Did you enter the NAS as local or remote connection?

I do not open the Access from internet

How is the Android device connected to the network (wifi, VPN, etc)?
Can you reach the server from the browser on your Android device?

Android device is connected on wifi.
I Can reach openHab from this device.
In openHab Android app if I select parameters/openHab server, local is connected and distant not set
However the app display the error: connection to local server failed.