Pop up notification about an app not using cellular data, even when using WiFi

Every time I open certain apps (Netflix, Instagram, for example), I get a pop up notification telling me that cellular data is turned off for that app. The thing is, I'm always on Wi-Fi when it happens, so I'm not using cellular data. Then I hit "OK" and the app works as normal. It's just highly obnoxious, because I KNOW cellular data is turned off for some of my apps, but the warning is pointless to me when I'm on Wi-Fi. I tried turning my phone off and on, and it didn't help. In the image, you can clearly see that I'm using Wi-Fi. Is anybody else having this problem? Is there any way to fix it without having to turn on cellular data for those apps?