How to fix error rpc-s-unsupported-authn-level in Windows 11

Solution Steps

1. 1 Press Windows key + R, type 'wf.msc' and press Enter to open Windows Firewall with Advanced Security. This is where you can manage firewall rules that might be blocking RPC traffic.
2. 2 In the left pane, click 'Inbound Rules'. Look for rules related to 'Remote Procedure Call (RPC)' or 'Windows Management Instrumentation (WMI)'. Ensure they are enabled. If not, right-click and select 'Enable Rule'.
3. 3 If the rules are enabled, check the 'Scope' tab of each rule to ensure that the remote IP addresses are allowed. You can also temporarily disable the firewall to test if it's the cause, but re-enable it after testing.
4. 4 Press Windows key + R, type 'gpedit.msc' and press Enter to open Local Group Policy Editor. Navigate to Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options. Find 'Network security: LAN Manager authentication level' and set it to 'Send NTLMv2 response only' or higher. This ensures compatibility with modern authentication.
5. 5 If the issue persists, check the RPC service. Press Win+R, type 'services.msc', and ensure 'Remote Procedure Call (RPC)' is running. Also, check 'DCOM Server Process Launcher' and 'RPC Endpoint Mapper' services.
6. 6 Finally, test the connection again. If it still fails, use the command 'dcomcnfg' to open Component Services, navigate to Component Services > Computers > My Computer > Properties, and check the 'Default Properties' tab. Set 'Default Authentication Level' to 'Connect' or higher, and 'Default Impersonation Level' to 'Identify'.