Referencing your duplicate post, this is by design - you are likely recycling the DevNonce and duplicates are rejected by the LNS. For development work you can turn this off in the console or you can make your version aligned with LMIC which does NOT support v1.0.4 incrementing Nonces.
Edit 11 Jan: failed to include NOT in the last sentence - LMIC doesn’t support incrementing DevNonces as required for v1.0.4 so you MUST use v1.0.3