"Error 691" Error Message When You Try to Connect to Your ISP
Verify Your User Name and Password
Make sure that the CAPS LOCK key has not been accidentally pressed and engaged while typing Password.
Click Start, point to Connect To, and then click your dial-up connection.
In the Connect dialog box, verify that your user name and password are correctly typed in the User name and Password boxes as provided by your ISP.
Verify the Phone Number
Verify that you are using the correct phone number to connect to your ISP.
Allow Unsecured Password
Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
Click the Security tab, and then verify that Typical (recommended settings) is selected.
In the Validate my identity as follows box, verify that Allow unsecured password is selected.
Click the Options tab.
Click to clear the Include Windows logon domain check box (if it is selected), and then click OK twice.
Check For Phone Line Noise.
If there is Noise in Phone Line call the phone company to check the phone lines.
Lower the Connection Speed
Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
Click the General tab, click your modem in the Connect Using box, and then click Configure.
In the Maximum speed (bps) box, click 9600, and then click OK twice.
Disable Hardware Flow Control
Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
Click the General tab, click your modem in the Connect Using box, and then click Configure.
Click to clear the Enable Hardware Flow Control check box, and then click OK twice.
Disable Modem Error Control
Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
Click the General tab, click your modem in the Connect Using box, and then click Configure.
Click to clear the Enable Modem Error Control check box, and then click OK twice.
Disable Modem Compression
Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
Click the General tab, click your modem in the Connect Using box, and then click Configure.
Click to clear the Enable Modem Compression check box, and then click OK twice.
Disable Software Compression
Click Start, click Control Panel, click Printers and Other Hardware, and then click Phone and Modem Options.
On the Modems tab, click the modem that you want to configure.
Click Properties.
Click the Advanced tab.
Click Change Default Preferences.
In Data Connection Preferences, click Disabled in the Compression list.
Disable LCP Extensions
You may have trouble connecting to your ISP if your ISP's Point-to-Point Protocol (PPP) server does not support Link Control Protocol (LCP) extensions.
To disable LCP extensions, follow these steps:
Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
On the Networking tab, click Settings, and then click to clear the Enable LCP extensions check box.
Disable IP Header Compression
You may experience issues logging on to your ISP if you are using IP header compression (also known as Van Jacobson, or VJ, header compression). To disable IP header compression, follow these steps:
Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
On the Networking tab, click Internet Protocol (TCP/IP), and then click Properties.
Click Advanced, and then click to clear the Use IP header compression check box.
Click OK.