Not locking on

[Ckirkhum]

If I walk up to the extender my phone will not lock on. If I go to the router and lock on there first then the phone will lock on to the Extender when going to that area.

[plemans]

What router do you have? 

What extender do you have? 
What do you mean by locking on? Connecting to it via wifi? 

You didn't give much details to go off