nginx fails to load ssl certificate

You should never share your private key. You should consider the key you posted here compromised and generate a new key and signing request.

You have a certificate request and not an actual signed certificate. You provide the request ('CSR') to the signing party. They use that request to create a signed certificate ('CRT') which they then make available to you. The key is never disclosed to anyone.

FYI, you can validate the keys just calling:

openssl x509 -noout -text -in your.crt
openssl rsa -noout -text -in your.key

In my case this error proved rather subtle: the BEGIN block started with 4 dashes, not 5. ---- vs -----. Sadly the validation tool error messages aren't very specific.