Android devices with issues to connect through wifi

I'm facing issues when the android devices on the company try to connects to the wireless network. Each day they must forget and add again the network since, regardless they are connected to the wifi, the devices keeps sending the traffic over the cellphone network and never shows up the banner to keep using the same network to authenticate later with the network agent when the network is saved on the device. Also, the captive portal never pop up on the android phones.

Any idea why is this happening? Any missing configuration on XG firewall?

Note: This behavior happends over different Android versions.

Thanks.