After isolating the problem to the BT Smart Hub 6 by successfully detecting the printer on both the iOS devices with all

three connect to the customer's previous BT HomeHub 4, resolved the issue by separating the BT Smart Hub 6's 2.4

Ghz & 5 Ghz wireless signals under separate SSIDs (5 Ghz has a "-5" suffix). With the iOS devices now definitely connected

to the 2.4 Ghz signal (would have to be manually connected to switch to 5 Ghz following the separation of signals), they

successfully detected the printer once more.