same thing happened to me once. My colleague at work told me that routers only have a certain anmount of things they can connect to before (he said in the order of 25) before they start going wrong. it's very easy to get up to 25 things, Phones, laptops, kindles, phones, smart tv, smart plugs, voice assistance, fridges, kettles, visitors and so on. I'm with virgin and called them with the intention of asking for a new router, but they told me there was a problem in my area with the signal they were working on. When the signal was fixed, the router could see everything. It led me to believe what the bloke said was botox. I think I put a q about it on here