ideally the output it prints when you are running it with the --debug option, at a minimum though the complete output it gives when you run it nornally ( rather than an edited single line ) .
Or, did you run openssl yourself in order to verify the certificate? I guess it would need the issuer certificate in chain.pem as well in order to confirm the leaf certificate’s validity.
OpenSSL is a great library for matching keys to certificates
You do need to understand how it works though
There are 2 types of keys which you will encounter on your LetsEncrypt process
A) An account key (what you use to sign all requests to LetsEncrypt)
B) a Web Key (what you use to sign the CSR and encryption activities once cert is avaialble)
when you are running the comparison which key are you using
I suggest that you paste the entire output, as a quoted block-of-code, from (and, including) the command-line prompt and your command, all the way through to everything that it produces when the --debug option is used.
It might also be helpful to include ls -l (filename) output so that we can see how long the files are, that you (think that you) are referencing in that command. Folks around here will know if that file-length doesn’t jive …
Thank you for giving your input. The issue is now resolved. Actually i was comparing the private.key with the cert.pem and error occurred. I reinstalled the key and this time concatenated the root file text correctly. The error is now no more but thank you for kind input.