This is because it is missing one or more required fields or the CSR contains non-alphanumeric characters in the required fields.
Related posts:
The CSR cannot be decoded. What does that mean and what should I do?
What should I do if I receive a ‘CSR invalid’ error during the certificate activation process?
I have noticed something incorrect in my CSR. What should I do?
Do I need to provide my business verification document again for renewing my OV/EV SSL certificate?
