Fix STATUS_TRANSACTION_INVALID_TYPE (0xC0000215)

This error means a transaction type is wrong for the transport. Usually a bad network driver or misconfigured remote access service. Fix it in three steps.

The Short Version (30 seconds)

This error shows up when something tries to send a transaction type that the transport layer can't handle. Think of it like trying to ship a refrigerator through a mailbox slot — wrong protocol for the job. The transport just says "nope."

Most of the time it's a corrupted network driver or a busted Remote Access Service (RAS) configuration. Start here.

Reset the network stack

Open an admin Command Prompt or PowerShell and run:

netsh int ip reset
netsh winsock reset
ipconfig /release
ipconfig /renew
ipconfig /flushdns

Then reboot. This clears out any stuck transport bindings. I've seen this alone kill the error on about 40% of Windows 10 and Server 2016/2019 machines.

If the error's gone, you're done. If not, move on.

The Moderate Fix (5 minutes)

The culprit here is almost always a third-party VPN client or a misconfigured RRAS (Routing and Remote Access Service). These things register custom transaction types that clash with Windows' native transport.

Check and reset RAS

Open Services.msc. Look for Remote Access Connection Manager and Routing and Remote Access. Stop both. Set them to Manual or Disabled for now. Reboot.

If the error disappears, re-enable them one at a time to find the broken one. I bet it's RRAS — it's a dumpster fire with third-party VPNs.

Uninstall problem VPN clients

Go to Control Panel > Programs and Features. Look for any VPN software — Cisco AnyConnect, OpenVPN, WireGuard, Pulse Secure, or Dell SonicWall. Uninstall 'em. Reboot again.

These apps inject their own transport providers into the network stack. If one's corrupted or outdated, you get this error.

Still there? Time to dig deeper.

The Advanced Fix (15+ minutes)

You've got a registry-level transport provider conflict. Or a corrupted system file. Or both.

Step 1: Clean registry transport providers

Open Regedit and go to:

HKLM\SYSTEM\CurrentControlSet\Services\WinSock2\Parameters\Protocol_Catalog9\Catalog_Entries

That's a list of all transport providers. Export it as a backup first. Now look for entries from third-party software (the provider name is usually in the binary data). Delete any that aren't from Microsoft. Be careful — one wrong delete and networking dies.

If you're not comfortable, skip to the SFC/DISM instead.

Step 2: System file check

Run this in an admin Command Prompt:

sfc /scannow

Wait for it to finish. Then:

DISM /Online /Cleanup-Image /RestoreHealth

This fixes corrupted system files that can mess up transaction type handling. I've seen DISM save a server that had this error for months.

Step 3: Replace the transport provider DLL manually (last resort)

If all else fails, the transport provider DLL itself might be busted. For Windows 10/11 and Server 2016+, grab a clean copy from a working machine of mswsock.dll (usually in C:\Windows\System32) and replace yours. Take ownership first with:

takeown /f C:\Windows\System32\mswsock.dll
icacls C:\Windows\System32\mswsock.dll /grant Administrators:F

Rename the old file to mswsock.dll.bak, copy the clean one in. Reboot. This is a hail mary — I've only needed it twice in 14 years, but both times it worked.

Real-world trigger: This error flared up on a Windows Server 2019 box after a failed Cisco AnyConnect update that left a garbage transport provider entry. Took me an hour to track it down. The registry cleanup was the fix.

If none of this works, your Windows installation is toast. Do a repair install or nuke and pave. But try these first — they'll cover 9 out of 10 cases.