@naiaraz Thanks for the update.
Have you set up a static IP address on the laptop or Did you change the LAN IP of Deco to be 192.168.173.1?
Could you please refer to this link and try to ping the LAN IP-192.168.173.1 to see what happened?
And Does Neither 2.4ghz nor 5ghz work on the AVELL laptop?--You could try to enable guest network for 2.4ghz only to have a test.
Have you tried to update the wireless driver on the laptop?
By the way, I see this laptop has an Ethernet port and would it work with Deco via Ethernet connection?
Please also check there is no device under Blacklist and no parental control profile has been set on this laptop.