SSL - heroku certs: add - no certificate

Question

I am having difficulty adding an SSL certificate to my hosting domain.

I previously uploaded the certificate, but for a bare domain (i.e. without www). I need to upgrade this to www domain. The command that I run is as follows:

heroku certs:add ../server.crt ../server.key --app [app name]

However, I always get the answer:

Resolving trust chain... failed
 !    No certificate given.

I generated the key and certificate several times, but always get the same answer. I would appreciate help in understanding where I might be wrong.

My certificate and key files exist (in the parent directory) as follows:

server.crt

Web Server CERTIFICATE
————————

——BEGIN CERTIFICATE——
[Certificate string]
——END CERTIFICATE——


INTERMEDIATE CA:  
———————————————————

——BEGIN CERTIFICATE——
[Intermediate CA]
——END CERTIFICATE——

server.key

-----BEGIN RSA PRIVATE KEY-----
[private key]
-----END RSA PRIVATE KEY-----