Fix RPC_S_INTERNAL_ERROR (0X000006E6) on Windows Server

30-Second Fix: Restart the RPC Services

This is the first thing you try. Open an elevated command prompt (Run as Administrator) and run:

net stop RpcSs && net start RpcSs
net stop RpcEptMapper && net start RpcEptMapper

That restarts the two core RPC services: the Remote Procedure Call (RPC) service and the RPC Endpoint Mapper. If the error popped up after a recent patch Tuesday or a reboot that went sideways, this alone often clears it. I've seen this work on Windows Server 2019 and 2022 when the error shows up in Event Viewer with event ID 5719 or 10010.

If the services won't stop or start, note which one fails — that's your real problem. Move to the next section.

5-Minute Fix: Check RPC Port and Firewall Rules

The culprit here is almost always a blocked or misconfigured port. RPC uses port 135 for the Endpoint Mapper, and dynamic ports in the range 49152-65535 for actual communication. If a firewall — Windows Firewall, a third-party app, or a hardware appliance — is blocking those, you'll get 0x000006E6 when trying to connect from another machine or when a service tries to register an endpoint.

Here's what you do:

1. Open Windows Firewall with Advanced Security.
2. Check inbound rules for "Remote Service Management" or "COM+ Network Access". Both need to be enabled.
3. If you're using a static RPC port (some admins lock it down), verify the registry key exists:

HKLM\SOFTWARE\Microsoft\Rpc\Internet
Key Name: Ports
Value: REG_MULTI_SZ with your port range (e.g., 50000-51000)

If that key is present, make sure your firewall allows those ports inbound. Also check the PortsInternetAvailable and UseInternetPorts values in that same key — they should be set to Y.

Don't bother checking DNS first. That rarely causes this specific error. Save that for when you see RPC_S_SERVER_UNAVAILABLE instead.

15-Minute Advanced Fix: Repair DCOM Permissions and Re-register Components

If the first two steps didn't work, something's busted in DCOM. The 0x000006E6 error can happen when a service or application doesn't have the right launch/access permissions for a COM object. This is more common on servers where someone's been tweaking security templates or running third-party installers that mess with DCOM settings.

Here's the step-by-step:

1. Open Component Services (dcomcnfg.exe).
2. Expand Component Services > Computers > My Computer > DCOM Config.
3. Right-click each problematic application (you'll see them if they have an error in the list) and choose Properties.
4. Go to the Security tab. For Launch and Activation Permissions, choose Customize, then click Edit.
   Make sure the following groups have these permissions:

Apply and restart the RPC services again.

Still broken? Time to re-register the key RPC DLLs. Run these from an elevated command prompt:

regsvr32 rpcrt4.dll
regsvr32 rpcss.dll
regsvr32 ole32.dll
regsvr32 oleaut32.dll

That re-registers the core COM/RPC libraries. I've fixed stubborn 0x000006E6 errors on Server 2016 this way after a bad Windows Update. Reboot afterwards.

One more thing — check if the error is tied to a specific application, like SQL Server or Exchange. Those apps sometimes have their own RPC endpoint configuration. For SQL, check the SQL Server Configuration Manager for the "SQL Server Browser" service — it needs to be running for remote connections.

If none of this works, you're looking at a corrupted system file. Run sfc /scannow and dism /online /cleanup-image /restorehealth. But that's rare — in 14 years, I've only had to do that twice for this error.