RPC_S_NO_PROTSEQS_REGISTERED (0X000006B2) Fix

You're staring at 0X000006B2 and wondering what broke

I've seen this error hundreds of times, usually on Windows Server 2012 R2 through 2022, but also on Windows 10/11 Pro machines running enterprise apps. The culprit here is almost always a deadlocked RPC service or a misconfigured DCOM interface. Let's get it fixed.

Step 1: Restart the RPC Services (the real fix)

Don't bother rebooting the whole server unless you have to. Just do this:

1. Open an elevated command prompt or PowerShell as Administrator.
2. Run these commands in order:

net stop rpcss
net start rpcss
net start DcomLaunch
net start RpcEptMapper

If the RPC Endpoint Mapper (RpcEptMapper) is already stopped, start it. The protocol sequences (like ncacn_ip_tcp or ncalrpc) are registered here. If this service doesn't start, you'll get 0X000006B2 instantly.

When services don't start

Check Event Viewer under Windows Logs > System for event ID 7034 or 7031 related to RPC. Common cause: the RPC service depends on the DCOM Server Process Launcher. Make sure that service is running too.

Step 2: Verify DCOM Permissions

The error also fires when DCOM permissions block the registered protocol sequences. Here's where I've seen it bite people: after a security update or group policy change.

1. Open Component Services (run dcomcnfg).
2. Go to Component Services > Computers > My Computer.
3. Right-click My Computer and pick Properties.
4. Go to the COM Security tab.
5. Under Access Permissions, click Edit Default.
6. Make sure Everyone and LOCAL SERVICE have Remote Access allowed. If not, add them.
7. Under Launch and Activation Permissions, repeat the same.

After changing permissions, restart the RPC services again. This has fixed the error on three separate customer sites this year alone.

Why this works

The error code means the RPC runtime has no protocol sequences registered — no transport protocols like TCP or named pipes to listen on. When the RPC service or the endpoint mapper hangs (often due to a locked registry key or a crashed dllhost.exe), those sequences aren't published. Restarting the services re-registers them. DCOM permissions control who can use those sequences. If permissions are missing, the sequences exist but are invisible to clients.

Less common variations

Sometimes the issue isn't the services themselves but a firewall rule blocking RPC dynamic ports. RPC uses port 135 for the endpoint mapper, then allocates transient ports (usually 49152-65535) for actual communication. If a firewall blocks those high ports, you'll see 0X000006B2 on the server side.

Quick check: Run netsh rpc show to see registered protocol sequences. If it's empty, you're definitely dealing with a dead service. But if it shows TCP on port 135 but no dynamic ranges, check Windows Firewall with Advanced Security for block rules on the RPC Dynamic Port range.

Another variation: MSDTC (Microsoft Distributed Transaction Coordinator) can trigger this error if it's misconfigured. I've seen it on SQL Server clusters. Check dcomcnfg > Component Services > Computers > My Computer > Distributed Transaction Coordinator. Ensure the service is running and network DTC access is enabled (under Security Configuration).

Prevention

Three things:

1. Keep DCOM permissions consistent — use Group Policy to lock them down rather than random manual changes.
2. Monitor RPC service health — set up a scheduled task or an alert on event ID 7034 for the RPC service. When it crashes, restart it automatically.
3. Don't over-block firewall ports — if you need to restrict RPC, use RPC over HTTPS (RPCHTTPS) or restrict the port range via netsh int ipv4 set dynamicport tcp start=49152 num=16384 and open only that range. Don't block 135 entirely.

That's it. You'll probably fix this in under 10 minutes. If not, check for third-party security software — I've seen McAfee VSE and Symantec Endpoint Protection kill RPC protocol sequences by hooking into the RPC runtime. Uninstall or disable them to test.