Apps Wifi device connected will not allow mobile data

[Donny Tarter]

I am developing an app to use a fingerprint scanner. The scanner connects to the phone via Wifi. When it's connected I do not know how to get the phone to use mobile data at the same time for internet. Even if there is a setting on the phone I could change which I cannot find I will need this to be auto or done via code. I tried setting mobile data always active in dev options but still same results.
Please Help