2w yrs ago installed 5 M4r units complete with the IOS app.  Set up as AP units radially fed off a Netgear Gb switch via ethernet Cat6 cables. All worked well until we had Gigaclear Fibre installed to the house which uses a Linksys router. 

Now, 1 unit has stopped working and I have discovered that the app has mainly stopped working. That is ....I open the app and whilst the wifi network is listed at the top, none of the TP units are listed in the overview section and when clicking 'More' all I see is two button, one for 'Router Settings' and one for 'Homecare'  All the wifi settings have diappeared.

If I tap on the 'world' icon I get a page saying "Some Decos are experiencing problems. One (the first one I bought has a "Main Deco" label and is the only one NOT experiencing problems. 3 others state "Disconnected from other Decos".  

Strangely, the wifi network appears to be working.  It does however appear to be around 50% slower than previously.

With the unit that no longer works, (and not listed in the Deco App) I have reset it but all that now does is sit there with a pulsoing blue light and of course I can't do anything with it.  I've deleted the app and reloaded it, logged into account but nothing changes - still no functions.

Anyone any ideas where to go next ... apart from scrapping the lot and buying Linksys.