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Its an app called "Network Signal Refresher Lite". Download and run it, then hit refresh on it and right after turn on mobile hotspot via a notification tile while its refreshing. Tethering will turn on even if your carrier checks for subscription, which I assume you dont' have. Don't tell anyone about this obvs.
I skimmed through the forum post and I didn't see any mention to using foxfi. Did you install Network Signal Refresher? It sounds like all you need to do is to run the app and quickly enable HotSpot option through the android settings menu.
this approach just worked for me with this app "Network Signal Refresher Lite" https://play.google.com/store/apps/details?id=com.atejapps.networksignalrefresher&hl=en
Android 7.0 Nexus 6p making the hotspot with FoxFi/pdaNet
:/ you could try something like this maybe... https://play.google.com/store/apps/details?id=com.atejapps.networksignalrefresher Might cause extra battery drain.