the things node help needed, sparkfun pro controler

i cant get "the things node" to work. i get this message:

Sending: mac join otaa Join not accepted: denied Check your coverage, keys and backend status. Sending: mac join otaa Response is not OK: no_free_ch Send join command failed

over and over again. i have coverage, because i made my own single channel gateway on my raspberry pi. and i have entered my keys correctly, i followd this instruction: can someone help me ?