The WR710N has been in place and working fine a long time as a CLIENT giving wireless access to a printer via an ethernet cable attached to the WR710N

Recently added a new main router (BT Smart Hub 2)

Trying to relink WR710N wirelessly as a CLIENT to the new router 

I am stuggling though

I can access the WR710N wirelessly after resetting the device 

After reset it goes in to WIRELESS ROUTER mode

When I try to change to CLIENT mode after entering the ROOT SSID of the new router and the wifi password, SAVE and REBOOT

The 710N either stays as a wireless router or becomes unreachable requiring a reset

Please can to assist - how tdo switch to client mode 

Thanks

JEremy