Ethernet working but wifi does not work

wifi dropped from last night and I couldn't connected wifi because I don't see my wifi on the list, I checked my every other devices and none of them works.
I tried to restart the router, it didn't show up on the wifi list. 
I tried to factory reset the router, wifi didn't work. 
so I chat with the agent and got to talk to the tech to exchange the router at the nearest branch. 
I went to do the exchange right away and setup the new router 
The wifi works for like 5 mins then went back to solid orange -> flashing orange -> solid green -> flashing green -> solid white -> flashing white
it keeps dropping and reconnecting over and over again 
then I chat with the agent again, they did me a test telling me it's gonna work after one hour when the system updates. 
one hour later it was not working like before . it's back to the no wifi showing phrase but ethernet works. 
I need internet for work , can anyone help ?