I have been having trouble with my phone and upstairs smart tv connecting to my wifi. This problem just started happening but I never had this issue before. My smart tv downstairs however, has no issue and still connects to my wifi.
What router or gateway are you using? Which band 2.4GHz or 5GHz? 2.4GHz has a longer range but much more interference. I would try switching bands if the devices can handle it, also switch channels. On the 2.4GHz band, try channels 1, 6 and 11, see if any one works better than the others. If all else fails, you may need a range extended. You can pick one up at any technology store like Amazon, Newegg, Best Buy, etc.