Problem with TemporaryKey.pfx I don't have the password

I went to Project Properties --> Signing tab--> then signed my app using the certificate in the ClickOnce section. In my case, the build was successful.

If PFX is password-protected, you can do little about this if you don't have a password. PFX contains a certificate with corresponding private key and optionally one or more CA certificates. Was the certificate in question self-signed or it was issued by some CA? I guess it was self-signed, considering it's file name. So you just create another certificate and use it instead of the old file.