When you choose EP Logon with Browser and click OK after giving the credentials, this error occurs.
This error is caused if either the network response is slow or the SAP Server response is slow (for example due to server load).
There is a SAP environment variable, RFC_CONNECT_TIMEOUT, to control the SAP Logon timeout period which is 60 seconds by default. Setting this variable to a larger value like 120 or 180 will reduce or completely remove the chances of getting timeout. The T-code RZ11 can be used to see the SAP environment variables.