New Post: Own certificate with openssl

I just generated a openssl certificate (4096 bits) as a password protected pfx file.
WPP doesn't want to import this certificate.
I tried to do it directly into the local computer/WSUS storage. Without any problems. Windows imports it. The only difference I see is the intended purposes: it's not "Code Signing" but "<All>".
Does this have an influence?

Thanks for your help.