I have a Plusnet Hub1 router that has been functioning for several years.  I have a wifi signal analyser app that has been showing 2 x 2.4GHz signals and 2 x 5GHz signals - one each from the router and one each from the extender.  Over the past few days the app has only been showing one 2.4 signal (assumed from the router, as it is much stronger next to it.).  It still shows 2 5GHz signals.  The only thing that has changed is that about 1 week ago a Plusnet technician 'split the wifi signal' (his words) to try and overcome a wifi intermittent glitch.  Immediately after his efforts I still had all 4 wifi signals on the app, it is only in the past 2 days I've noticed the disappearance of the 2.4 signal from the TP link extender.  Has the SSID(?) been changed and should I try to reset the extender to get it back. Or is there likely to be some other problem?