NIC gets the TCP Sync request but no ACK sent back

My setup has two NICs. NIC 1 is the primary interface and connects to my router under 192.168.1.x. NIC 2 is a high-speed connectX-3 interface directly connected to my PC under 10.10.10.x. The setup was working properly before, except sometimes I have to reset the NIC 2 when it overheating. Since last week, I can’t visit anything from NIC 2, but I haven’t changed anything. I’ve tried to replace it with a new card of the same model, reset all configs, and rebuild the system, but nothing helps.

NIC 1 still works perfectly without any issues. But I can’t visit the web UI page or connect to SMB through NIC 2.

Ping from NIC 2 to PC or from PC to NIC 2 works fine. After checking with tcpdump, I found the TCP Sync requests reached the server, but there is no Sync Ack sent back.

I don’t understand why that happens and don’t know what to investigate further. Can somebody help?

Btw, I checked the “iptables”, and there is no firewall rule since the system was just rebuilt.