Smart bulb won’t connect to hub 5

Looking for help!! Recently bought 3 new Tcp smart bulbs. And having a right carry on getting them to connect. After hours of trying to connect and searching the internet for help! Tried the suggestion of turning off 5ghz to only 2.4ghz. Which still didn’t help 😐

I managed to get them connected using my phones hotspot 👍🏻

But then when I reactivated the 5ghz they became off line and couldn’t connect to server.

My parents had the same problem with there smart plugs when they upgraded there router but I didn’t have nearly enough trouble with there’s as I am with mine!

What am I missing! Can anyone help before I throw the router box out the window 🙃

Thanks 🙂