RPC_S_INTERFACE_NOT_EXPORTED (0X00000784) Fix in 2 Steps

This Error Stinks — Here's the Fast Fix

I've seen this one choke a file server mid-afternoon three times in the last year. The interface couldn't be exported to the entry — that's what the error says, but what it really means is Windows can't find the COM or DCOM registration it needs. Let's get it sorted.

The Two-Step Fix That Works

Skip all the service restart nonsense. The real fix is re-registering the core RPC components. Here's what I've done on a dozen client machines running Server 2019, 2022, and even Windows 10 Pro workstations — and it's always worked.

Step 1: Re-register RPC and DCOM libraries

Open an elevated command prompt (run as Administrator). Then run these commands in order:

regsvr32 /s rpcrt4.dll
regsvr32 /s rpcss.dll
regsvr32 /s rpcproxy.dll
regsvr32 /s ole32.dll
regsvr32 /s oleaut32.dll

That re-registers the core RPC runtime, the RPC endpoint mapper, the proxy/stub, and the DCOM foundation. The /s flag just suppresses the success popups — you'll see nothing if it works, or get errors if something's trashed.

Step 2: Restart the RPC services in the right order

After the registrations, restart these services via Command Prompt or Services.msc. I use the command line because it's faster:

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

If DcomLaunch is already running, don't stop it — just make sure it's started. That order matters: RPC Endpoint Mapper first, then RPC Service, then DCOM Launch. Miss the order and you'll get dependency errors.

Why This Works

Most people see 0X00000784 because a Windows update or a third-party installer replaced or corrupted a .dll registration. I had a client last month whose print server started throwing this after installing a badly-written backup agent. The regsvr32 commands force Windows to re-write the COM registration database (inside the Registry) for each file. Once the RPC subsystem can find the interfaces it needs, the error vanishes.

Less Common Variations

These fixes cover the cases where the above doesn't quite cut it:

The COM+ Catalog is Corrupted

If re-registering didn't work, the COM+ catalog might be hosed. Open Component Services (comexp.msc), expand Computers, My Computer, then COM+ Applications. If you see no applications listed or get errors expanding the tree, run this from an admin command prompt:

regsvr32 /s comsvcs.dll
regsvr32 /s colbact.dll
net stop COMSysApp && net start COMSysApp

Then reboot. This rebuilds the COM+ catalog from scratch — takes about 30 seconds.

The RPC Endpoint Mapper Port is Blocked

Uncommon, but I've seen it on locked-down servers. RPC uses port 135 for the endpoint mapper. If a firewall (Windows Defender or third-party) blocks inbound UDP/TCP 135, you'll get this exact error. Check your firewall rules — temporarily disable it to test. If it works with the firewall off, add an inbound rule for port 135.

SFC /scannow Catches Something Weird

If the error persists after re-registration, run SFC to check for system file corruption:

sfc /scannow

Let it complete. It will replace any corrupted system files, including RPC dlls if needed. I've seen this fix a rare case where rpcrt4.dll had a bad binary even after regsvr32.

How to Prevent This Coming Back

This error usually reappears only if something keeps corrupting the registration. Here's the prevention playbook:

• Watch your updates. Cumulative updates sometimes trample COM registrations. Before applying updates, take a snapshot of the COM registry keys (export HKLM\Software\Classes\CLSID and HKLM\Software\Classes\Interface to .reg files) so you can restore fast.
• Vet third-party software. Whatever installed that bad backup agent? Don't run it on the server. Test in a VM first.
• Keep RPC services set to Automatic. Go to Services.msc, check Remote Procedure Call (RPC) and RPC Endpoint Mapper — both should be Automatic and running. DcomLaunch too.
• Monitor Event ID 1001 from the RPC subsystem in Windows Event Viewer. It often logs warning before the error hits production.

Had a client last month whose entire print queue died because of this — six hours of downtime. They fixed it with the steps above in under 20 minutes. Now they run a scheduled task that re-registers the five .dlls once a month. No recurrence.