Yesterday my phone started giving me issues with staying connected to my home wifi. I've contacted my internet provided and it's not them. I think the Verizon security app updated a day or two ago and that's when the issue started.
I had that problem with my S5 one of the things I was told to try was going into settings-backup and reset-reset network settings. It will reset blue tooth mobile data and wifi. You will have to set them all up again with passwords and what ever but it may help. Also I was told to go to application manager-WiFi direct-storage and tap on clear data. You might want to try this one first it should just clear the settings for your wifi not mobile data or blue tooth. You will have to put your password back in for the wifi