Comodo Essentials SSL: Vestacp “SSL intermediate chain is not valid”

Question

I'm trying to install Comodo Essential SSL via Vestacp here's that I did. I opened www_example_com.crt and copied the digest and pasted it into SSL Certificate box then opened www_example_com.key used to generate the ssl at the beginning which starts with -----BEGIN PRIVATE KEY----- and pasted the digest into SSL Key box then copied the digest of the other 3 files in this order into one file and copied the whole digest and pasted it into SSL Certificate Authority / Intermediate box but I get SSL intermediate chain is not valid

AddTrustExternalCARoot.crt
USERTrustRSAAddTrustCA.crt
SectigoRSADomainValidationSecureServerCA.crt

Final digest looks like this

-----BEGIN CERTIFICATE-----

-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----

-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----

-----END CERTIFICATE-----

I checked the certificate and the key and have no issue using https://www.sslshopper.com/certificate-key-matcher.html

I restored a back up so the key file doesn't exist on the server now does it matter? It's the first time I try to install SSL so please assist. Thanks in advance.

Answer 1

The Authority digest must be the content of these files in this order

SectigoRSADomainValidationSecureServerCA.crt

AddTrustExternalCARoot.crt 

USERTrustRSAAddTrustCA.crt