Please update your gps.conf
If you're currently using app_gps and reporting to APRS with it, please read this:
app_gps default server configuration in app_gps.c points only to a single APRS-IS server (second.aprs.net). That server is currently full most of the day (300 users) and does not accept new clients. Due to outages on other servers it has been full for several weeks, leaving some users out, probably including some app_gps users who are only trying to connect second.aprs.net.
Please update your gps.conf to say either:
server = rotate.aprs2.net
port = 14580
server = rotate.aprs.net
port = 14580
rotate.aprs.net points to all 9 APRS-IS core servers (2 of those down currently), and using that will get you automatically connected to one of those (not just the second in row which is currently full).
If you choose to use rotate.aprs2.net, you will end up on one of over 80 Tier2 servers which have a Dynamic DNS setup (rotate.aprs2.net always points to a smaller subset of servers which have been tested and verified to be available and not full right now).
This way you'll get connected even if second.aprs.net would happen to be full or down (and it wouldn't be full if everyone used the rotate addresses, anyway).