A failed TCP connection can be caused by any number of things. Normally a firewall somewhere between the two machines or the remote machine has been disconnected.
If the application isn’t responding quickly that could be registered as a failed connection attempt. That slow response could be caused by database slowdown, disk slowdown, CPU load, etc.
Just looking at the Failed Connection Attempts won’t give you a lot of troubleshooting information.
Connection failed means the client attempted a TCP handshake with another host and the 3-way handshake was either not completed (SYN – SYN/ACK – ACK) or a RST was sent indicating that the service was not listening on that port. This is a normal part of TCP operation and is likely not creating any performance issues.