If your Certificate Signing Request (CSR) is rejected when attempting to activate an SSL/TLS certificate, follow these steps to troubleshoot and resolve the issue:

1. Verify CSR Format: Ensure that the CSR starts and ends with exactly five dashes before and after -----BEGIN CERTIFICATE REQUEST----- and -----END CERTIFICATE REQUEST-----, respectively.

2. Check Country Code: Confirm that your country code is a valid two-letter ISO 3166-1 code (e.g., US for the United States, GB for the UK). Use the correct code based on your location.

3. Ensure Minimum Bit Length: The CSR must be at least 2048 bits long to meet security standards. If it's shorter, you may need to regenerate the request with a longer length.

4. Review Password Usage: If a password was used during CSR generation, ensure it contains no special characters. This is crucial for the subsequent SSL installation process.

5. Examine Subject Alternative Names (SANs): For non-UCC certificates, include necessary SANs like DNS names in the correct format (e.g., www.example.com). Ensure they are accurately listed.

6. Check Header and Footer: Verify that the exact header and footer lines with five dashes each are present without any trailing spaces.

7. Handle Renewal Carefully: If renewing, ensure the common name (domain) matches exactly as it did in the original certificate to avoid rejection.

8. Use Text Editors for Checking: Before submitting, paste your CSR into a simple text editor to check for formatting issues and ensure there are no unintended characters or spaces.

9. Save RSA Private Key: Remember to save the RSA private key generated alongside the CSR, as it's essential for SSL installation.

10. Contact Support if Necessary: If all checks pass and the issue persists, reach out to your Certificate Authority (CA) support for further assistance.