Trouble Connecting GB109 AC Remote to UPC COMPAL CH7465CE Modem/Router: 2.4GHz & 5GHz Tips

Hello, I have a question because for a few days I have been trying to connect the device enabling remote control of air conditioning in the apartment, namely GB109, but I have a problem when the application does not want to connect to the wifi network from UPC, and more precisely with one of their modem / router COMPAL CH7465CE.
If I make a router in the phone, it's okay, everything works, if I use a different modem / router, e.g. HITRON CGN4EU from UPC, everything also works and the device configures itself in a second. The difference between these devices is that the one with which the problem is 2.4GHZ and 5GHZ works with the same name and password, but it is not a problem to turn off 5GHZ in the 192.168.0.1 settings and it does not help even on the hotline, the technician changed the name of the 5GHZ network but also nothing. In this modem / router, these two networks are separated, i.e. two different names and passwords, maybe there is a problem here.
Maybe some of you have an idea what you can change the settings in this problematic router that will enable the connection, or maybe the easiest way will be to change it to another? Thanks in advance for your help, best regards

How do you force a connection to a given network name? Are you doing it through some app on your phone?

The connection is established via an application dedicated to this device.

Added after 7 [minutes]:

I will add that when starting the application - it finds the wifi network with which the phone is connected (this is of course a requirement) and it is enough to enter the password of this network and then it tries to pair (configure the device with the network but something is in the way).

@hosapartments
What software version in this CB?

Do not turn off the network, but give them two different names and two different keys.