The certificate was created with Certbot. I did not encrypt the certificate or key from Certbot. None of the files appear to be encrypted when viewed with a text editor (Notepad ++).
The site has been working fine for quite a while with a certificate from godaddy. Therefore, I presume the configuration is correct. As an experiment, when I use the new cert and chain with the old key, I get an error that the certificate and key do not match. When I use the old cert and new key I get the above error. This seems to suggest that the problem is with the key file from Certbot.
I also tried converting the key to RSA format as described here: Error adding cert, Invalid private key
Thank you for any help you can provide!