@Solla-topee Hi, thanks for the reply. The extender would not accept my router password at all. I reset the extender a number of times but it would never accept the password even though I know it is correct. Each attempt was made using the WPS method of set-up. I even connected to the extender IP address and still couldn't change the password.

However, I have now found a solution.

I used the 'Tether' App and then I could see the password in the set up. I changed the password from the encrypted default setting in the extender to the same as my router and now it works on both 2.4gHz and 5gHz bands.

The instructions make the WPS method sound so straightforward, and it would have been had the password been accepted.

Thanks again for trying to help :)

@Taff64 

I had the same frustrating problem using the WPS connection.  Managed to do it using the Tether app.  Not sure why that didn't work for you but make sure you reset the extender first and plug it in near your router. 

As well as the Tether app password you will be requested to enter a password for the extender. I suspect that you might not have reset it and that's why you got something encrypted. 

I was able to enter my router password for 2,4 frequency extension but had to skip the 5.  I subsequently went back in and it then accepted the same password.