Maybe coincidence, maybe not.
Sometimes a complete shutdown of a router will allow it to choose a different channel if it's current has become crowded. I had trouble with a couple of devices when my neighbours installed wifi while I was away for the weekend (router on, everything else off or with me
). Came back and had trouble with several devices (two tablets and an iPod) disconnecting. I checked the available networks in the wifi settings and noticed a new, quite powerful signal. Powered down everthing including the router, brought them back up (waiting at least 5min after powering the router) and all is back to normal.
Many tablets just don't have the power to get through a noisy channel just like a laptop does.
Note: the two affected tablets were not Kobos. My kids have the Kobos, and they are locked out of the wifi.