Have you gone into 'Settings' > 'Battery' > 'Optimise' and deselected the Notts County app? This should allow the connection to continue even when the rest go to sleep to save battery. I'm on Android 8 (Oreo) also on a Huawei (Mate 10 Pro) and it seems to work so far, amazingly!
I know in 7.0 the settings may possibly be laid out differently or named differently but worth a shot!