When you say "connect to wifi", do you mean you are trying to get a wifi device connected to the router or do you mean the internet connection is dropping out?
When a dropout occurs, what lights are lit on the NBN connection box and on the wifi router?
Do you have a computer connected by cable to the router? Does it get the same dropouts as your wifi device?
The DSL light on the router needs to be on before the internet light can come on.
Having the NBN box DSL light on means it is communicating with the NBN network. The router DSL light off may indicate a problem at the far end.
You can persist with online chat or wait for a moderator on this post.
Or make a new post with these extra bits of info added in.
Make the subject: Internet connection slow and drops out.