Fix 0x80093029 OSS API DLL Not Linked Error

You're setting up a printer on Windows 10 or 11 — maybe a Brother HL-L2370DW or an HP LaserJet Pro — and just as Windows finishes extracting the driver files, you get the error 0X80093029: OSS_API_DLL_NOT_LINKED. The printer setup freezes or rolls back. I've seen this mostly after a Windows update that changed how the OS handles ASN.1 (Abstract Syntax Notation One) encryption, or after a driver was partially uninstalled. It's infuriating because the error message gives you nothing useful, just an obscure DLL reference.

Root Cause

The short version: Windows can't locate or link to the ossapi.dll file, which handles ASN.1 encoding for printer communication. This happens when:

The DLL is missing or corrupted (often after a Windows Update that replaced the file).
Your printer driver was designed for an older Windows build and expects a specific version of the DLL.
There's a registry entry pointing to the wrong path for the DLL.

I've also seen this on systems where third-party security software (like McAfee or Norton) quarantined the DLL as a false positive. The real fix is to restore the DLL and re-register it or replace it with a fresh copy from the Windows side-by-side (WinSxS) store.

Step-by-Step Fix

Check if ossapi.dll exists
Open File Explorer and go to C:\Windows\System32. Search for ossapi.dll. If it's missing, skip to step 4. If it's there, right-click it > Properties > Details tab to see the file version. Write it down.
Re-register the DLL
Open Command Prompt as Administrator. Type:
```
regsvr32 /u ossapi.dll
regsvr32 ossapi.dll
```
You should see a success message. If you get an error like "The module failed to load", the DLL is corrupted. Move to step 4.
Check the registry path
Press Win+R, type regedit, hit Enter. Navigate to:
```
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters
```
Look for a value named OSSAPIDLL or similar. If it points to a non-existent path, delete that value (right-click > Delete). This tripped me up the first time — the registry had a wrong path from an old driver install.
Restore the DLL from WinSxS
Windows keeps backup copies in the WinSxS folder. Open Command Prompt as Admin and run:
```
sfc /scanfile=C:\Windows\System32\ossapi.dll
```
This checks the DLL against the system cache. If it finds corruption, it'll replace the file. Then run:
```
DISM /Online /Cleanup-Image /RestoreHealth
```
Wait for it to finish (may take 10-15 minutes). Reboot, then try the printer setup again.
If still broken, grab the DLL from a working PC
On the same Windows version (e.g., Windows 10 22H2), copy C:\Windows\System32\ossapi.dll to a USB drive. On the broken PC, rename the corrupted one to ossapi.dll.old, then paste the fresh copy into System32. Re-register it with regsvr32 ossapi.dll.
Last resort: reinstall the printer driver from scratch
Go to Settings > Bluetooth & devices > Printers & scanners. Click on your printer, select Remove device. Then open Device Manager, find the printer under Print queues, right-click and Uninstall driver. Download the latest driver from the manufacturer's site (not Windows Update), run the installer as Admin. This forces Windows to rebuild the ASN.1 link chain.

Still Getting the Error?

Check if your antivirus has a quarantine log — look for ossapi.dll in there. Restore it if found. Also, if you recently uninstalled a VPN or security suite that hooks into network stack (like Kaspersky or Cisco AnyConnect), those sometimes remove shared DLLs. In that case, a system restore to a point before the uninstall often works. And if you're on Windows 11 24H2, note that Microsoft changed ASN.1 handling in that build — some older printer drivers need a compatibility update. Check the manufacturer's support page for a Win11-specific driver.