Not sure if this is related to this question (seems to be but I cannot comment only answer and I don\'t have one yet but would like to add my experience with this issue).
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You may not appear in herenow for a variety of reasons:
1) If a user checks in without a lat/lng, we consider that a record-keeping check-in and may not display the user in herenow since we have no idea if they are actually there or not
2) If the user checks in with a lat/lng that is sufficiently far away from the venue, we may not display the user in herenow.
Looking at your request, it would appear that you're not passing your current lat/lng to the API, which would likely put you in case (1).
The official app + 4th & Mayor should be passing your lat/lng as reported by your phone. The only reason I can think that herenow wouldn't update is if you're checking in to a venue you are not near to, or if your phone has a poor GPS look.
If you do start passing lat/lngs to the API servers, be sure that you are reporting the user's actual location as reported by an impartial device (like the phone's OS). Failure to do otherwise may cause your application to be disabled without notice.