Firstly when your issuance email arrives it will contain your web server certificate. Copy your web server certificate into a text editor such as notepad including the header and footer. You should then have a text file that looks like:
-----BEGIN CERTIFICATE-----
[encoded data]
-----END CERTIFICATE-----
Make sure you have 5 dashes to either side of the BEGIN CERTIFICATE and END CERTIFICATE and that no white space, extra line breaks or additional characters have been inadvertently added.