Sending an ACME HTTP validation request to rssl.ece.mcgill.ca results in an unacceptable redirect. This is most likely a misconfiguration of your web server or your web application.
It appears that a redirect was generated by your web server that is missing a trailing slash after your domain name: https://rssl.ece.mcgill.ca.well-known/acme-challenge/letsdebug-test. Check your web server configuration and .htaccess for Redirect/RedirectMatch/RewriteRule.
Trace:
@0ms: Making a request to http://rssl.ece.mcgill.ca/.well-known/acme-challenge/letsdebug-test (using initial IP 132.206.31.68)
@0ms: Dialing 132.206.31.68
@31ms: Server response: HTTP 301 Moved Permanently
@31ms: Received redirect to https://rssl.ece.mcgill.ca/.well-known/acme-challenge/letsdebug-test
@31ms: Dialing 132.206.31.68
@99ms: Server response: HTTP 302 Found
@99ms: Received redirect to https://rssl.ece.mcgill.ca.well-known/acme-challenge/letsdebug-test
A test authorization for rssl.ece.mcgill.ca to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
132.206.31.68: Fetching https://rssl.ece.mcgill.ca.well-known/acme-challenge/o4Xykyk5cY6CzJ5qAnfmWshs05j87hgEdyFutFRCINg: Invalid host in redirect target "rssl.ece.mcgill.ca.well-known". Check webserver config for missing '/' in redirect target.