Phone says it’s connected to my garmin watch (venu 2s), but the app garmin connect says it isn’t

I have a sort of similar, but minor issue with my Garmin Edge 130 Plus. Same scenario as yours, but when I leave the Garmin Connect app open, after few seconds the status changes from "Not Connected" to "Connected". What happens when you leave the app open for a while?

I would go into the Bluetooth settings on your iPhone and "forget" the Garmin device. Then in the Garmin Connect app, remove the Venu 2s from Garmin Devices. Restart the phone, place the Venu 2S in pairing mode, then pair using Garmin Connect.