I'm having the same behavior over here. Yesterday was OTAA accepted, this morning when I came back in the office it was denied. After a gateway reboot ( sudo systemctl restart ttn-gateway.service ), a OTAA join is accepted again.
Node: RN2483 on the microchip demo board (RN2483 1.0.1 Dec 15 2015 09:38:09)
Gateway: ic880A + Raspberry Pi 3 (Raspbian GNU/Linux 8 (jessie))
@lucas Did you fix this issue?
Any help is welcome
Bart