@Mdkhirul have you tried "Deco labs" feature from your Deco mobile app and see if it shows something? Deco labs will check channels interference, speed, signal strength., etc

the only problem with M4 so far is very limited user/admin interface. other than that im happy user. with the right cabling, M4 positioning and you connects all together as it shoul be M4 is working...

@JFil is your NIC card capable of such speeds?