The issue was, I was setting another class for the hostname. Now I used the exact same IP as the machine plus the 8080 port and it worked.
but after a day, when I restarted the machine, it doesn't work!
[*] Initializing Hak5 Cloud C2 v3.3.0
[*] Hostname: 192.168.0.17
[*] DB Path: c2.db
[*] Validating License
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[!] Internet Connection required to activate C2 License