Quick answer: Arma 3 won't start: read RPT log, update mods, check server.cfg and open ports 2302–2305 UDP.
If you landed here: Server crashes on start, BattEye/mod errors in logs or restart loop in panel.
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Frequently asked questions (FAQ)
Arma 3 server won't start – first steps?
Read RPT log (arma3server_x64_*.rpt). Common: mod version mismatch, BattEye error, bad server.cfg, port 2302 blocked.
Arma 3 mod mismatch?
Update all mods via Steam Workshop. Check mod list in server.cfg. Remove mods one by one to test.
Which ports for Arma 3?
2302 UDP (game) + 2303–2305 UDP. BattEye needs open UDP ports.