I get the error ERR_SSL_CLIENT_AUTH_CERT_NO_PRIVATE_KEY whenever I try to use a certificate to access a website.

If I try to troubleshoot the problem, it says "one or more network protocols are missing on this computer", but windows 10 always fails to fix it.

I use certificates to access my bank account and my school website. It worked fine until 1 week ago, when I wasn't able to use certificates anymore. Note that neither of the certificates are outdated and they both have private keys. Even if I pick the wrong certificate, I don't get an authentication error like I did before, but I always get the error shown above. I tried both certificates on different websites, where I kept getting the ERR_SSL_CLIENT_AUTH_CERT_NO_PRIVATE_KEY error, instead of the 403 - forbidden access error. That's how I know the problem is in Windows. (If I try to access the website without a certificate (clicking cancel when choosing a certificate) I get the forbidden access error, as shown in the following picture.)

Also, the issue is not in the router, because I tried accessing the internet on my PC via my phone's mobile network (usb tethering) and I got the same error.

I didn't install any new antivirus programs and I didn't change any firewall settings when I started getting the error. I even uninstalled my antivirus software but the issue is still here.

I have tried several fixes for the "One or more network protocols are missing", most of which caused the users to have no internet access, however, I was not able to find any cases, where the users only weren't able to use their certificates. The fixes included some adjustments to the registry, and "netsh" commands in the cmd, but none of them worked.

Can someone please tell me how to fix this. Due to the certificate error I am unable to access my bank account, so I am unable to make any payments. Please respond ASAP.

Edit: Just to prove that the certificate hasn't expired yet and that I do have the private key -

FIX:

Luckily found a backup of the certificate, reinstalled it and it works. Apparently the private keys got wiped somehow, no idea how.