What should I do if I receive a 'CSR invalid' error during the certificate activation process?

Detailed solution of this problem is given in article - CSR can not be decoded error?

If this happens, your common name is not appropriately formatted for your type of certificate (wildcard certificates should use *.domain.com, for example) or you could also have disallowed characters in other fields. Please create a new CSR that only use the English alphabet and numbers 0-9. For example, if the "&" symbol is included in your Organization Name, please type out "and" instead.