WiFi turns off when iPod is locked? iPod Touch | 5th generation | iOS 9.3.1

Hey, thanks for reading

Ever since a few weeks ago my iPod Touch 5G (iOS 9.3.1) has been disconnecting from the WiFi whenever it's locked. I have had this device for about a year and it has never done this until now. This happened all the time with my iPod Touch 4G (iOS 6.X.X) and it caused me to lose it for 4+ months because I couldn't use Find My Device. Anyone know how to stop this for my iPod Touch 5G?

I don't know why this happened, but recently I reset my internet and tried to connect when it was off and it let me connect when there was no internet. It was around this time it started happening, but I don't know if it's relevant.