Thanks for the responses, all..
My issue is that my Tapo and Ring devices are reporting that they are Offline in their respective Mobile Phone Apps. However, using VM’s Status Checker->Test WiFi Hub/Connected Devices shows that there are no Broadband Issues, and that they are all connected to my Hub (with Good connection/Strong Signal).
My understanding is that because Ring and Tapo devices are "cloud-based" any communications with the devices does not directly rely on the home network’s IP address (due to inherent levels of indirection). As such, I believe it is the "handshake" between my devices and the Ring/Tapo cloud servers that is failing. It is ‘interesting’ that the Tapo devices AND the Ring devices started being reported as Offline by their Apps (so presumably the Servers) at the same time, which would point to something untoward with the Router; hence the request for a Reboot.
I’m not sure why VM cannot reboot my Router given they can carry out the much more drastic action of a Reset (which, I repeat, I do not want!).