Daikin Atherma 3 Wlan adapted connection issues

Hello,
We recently bought a Daikin Atherma 3. We are having a problem connecting the WLAN adapter to our internet connection. We connected to the portable router without any problems, but with 5G stationary router we having problems, we had to split the connection into 5Ghz and 2.4Ghz - we connected to 2.4Ghz because it was stated that only this connection is acceptable. We have tried almost all the 2.4Ghz settings and they are currently as follows:
Network Mode - 802.11 b/g/n
Channel Bandwidth - 20Mhz (also tried with 20Mhz/40Mhz)
Frequency (Channel) - 2437Mhz (Channel 6) (also tried with channel 1 and auto (channe1-11))

Any help would be appreciated!