Error: The Underlying Connection Was Closed: Windows 11 Update

Issue:

A regression has been observed following the Windows 11 update released on October 15th. This update has introduced a bug that specifically prevents the opening of the Book Keeper web company file, which then throws a corresponding error message.

Solution - 1:

Steps to Disable HTTP/2 via Registry Editor

1. Open Registry Editor

1. Press the Windows key + R to open the Run dialog.

2. Type regedit and press Enter, or click OK.

3. When the User Account Control (UAC) prompt appears, click Yes to open the Registry Editor with administrative privileges.

2. Navigate to the HTTP Parameters Key

1. In the Registry Editor, navigate to the following path (you can copy and paste the path into the address bar at the top): HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters

3. Create and Set the EnableHttp2Tls Value

This step disables HTTP/2 for encrypted (TLS/HTTPS) connections.

1. In the right pane of the Parameters key, right-click on an empty space.

2. At the top, click on Edit > New, and then click DWORD (32-bit) Value.

3. Name the new value EnableHttp2Tls (case-sensitive).

4. Double-click the newly created EnableHttp2Tls value.

5. Ensure the Value data is set to 0. (This is the default for a new DWORD, and a value of 0 disables the feature).

6. Click OK.

4. Create and Set the EnableHttp2Cleartext Value

This step disables HTTP/2 for unencrypted (Cleartext/HTTP) connections.

1. Again, right-click on an empty space in the right pane of the Parameters key.

2. At the top, click on Edit > New, and then click DWORD (32-bit) Value.

3. Name the new value EnableHttp2Cleartext (case-sensitive).

4. Double-click the newly created EnableHttp2Cleartext value.

5. Ensure the Value data is set to 0.

6. Click OK.

5. Reboot the Machine

1. Close the Registry Editor.

2. Restart your computer for the changes to take effect.

Once the machine reboots, the HTTP/2 protocol should be disabled, potentially mitigating the issues related to the specified Windows Updates (KB5066835 / KB5066131).

Solution - 2:

If above solution doesn't work, simply remove Windows Update number: KB5066835

and reboot system.

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