@Tukatdalala 

A good rule of thumb is to always check the physical first. This means checking that the cable is connected firmly on both ends. Try a different port on the router, swap the cable out, try a shorter cable, and so on. Also, make sure the extender is firmly plugged into the wall outlet. When it drops off line check the lights on the extender and record the color status then look at the user guide to see what those colors indicate.  You can also check the router's logs to determine where the break in service is being triggered. 

  @Tukatdalala 

It would.  However, if the lights status does not change it is not likely an issue between the extender and the host router/AP.  It is likely clients are not able to determine which node to connect to, the host or the RE.  This usually happens in two cases.  1.  The extender is too close to the host and 2.  the SSID was clonned and the client can't determine which node to connect to so it either hops back and forth or just fails to connect.  

the solution is to change the SSID of the extender to something unique.  The password should remain the same as that is not changable, at least at this time.  Yes this will mean that devices will not automatically change.  But it should correct a concern like this.