When you change the password on the camera directly (via its web interface), you create a mismatch. The camera now knows Password B, but iVMS-4200 or your NVR still has Password A stored in its encrypted database. The result?

You are not alone. This is one of the most common, yet most misunderstood, Hikvision error codes. Most guides will tell you to simply "check your password." That is like telling someone with a flat tire to "check the air pressure." It is correct, but it is not helpful.

Save this guide. Next time you see that red error message, you won't panic. You will fix it. And you will fix it better.

A: Yes, but it is a nuclear option. It forces a default password (usually admin with no password or a QR code on the device). Use the fixes above first.

A: Indirectly. If the firewall blocks the SDK’s return packet, the DLL might interpret a timeout as a login error. Temporarily disable the firewall to test.

If you are reading this, you have likely been staring at a frustrating pop-up window displaying "HCNETSDKDLL 23" or a variation like Error Code 23: NET_DVR_PASSWORD_ERROR . You have probably tried restarting everything three times, yet the red light on your NVR or camera refuses to turn green.