Many applications will report that MacTCP is not installed or that it has been disabled if the connection attempt via MacTCP fails. This could be due to a variety of reasons.
First verify that the network you are connected to supports MacTCP. Next, the configuration information for the MacTCP control panel should be verified with your TCP/IP network administrator or internet service provider. If PPP or SLIP is being used, you would also need to verify that those components are in working order. If all this has been verified and the error still occurs, you may want to try making a connection with another application like MacTCP Ping.
Support Information Services