RBN is a bit tricky to get spotted 100% of the time, especially QRP or with poor band conditions. I find that if I call CQ 3 times and then callsign, instead of something like "CQ POTA", the RBN spotters have a tendency to pick me up easier. (i.e. CQ CQ CQ <call> <call> <call>). If you do this on the band and time you've scheduled an activation for on the POTA app it should work.
RBN is a bit tricky to get spotted 100% of the time, especially QRP or with poor band conditions. I find that if I call CQ 3 times and then callsign, instead of something like "CQ POTA", the RBN spotters have a tendency to pick me up easier. (i.e.
CQ CQ CQ <call> <call> <call>). If you do this on the band and time you've scheduled an activation for on the POTA app it should work.