Question:
When I am purchasing or replacing my certificate I get the error:
Your RSA key is too small! or This CSR uses an unsupported key size.

Answer:
For all certificates that Sectigo issues (including EV SSL), the RSA key size MUST BE at least 2048-bit as of 20-DEC-2010. To resolve this error please regenerate your CSR with the key size of 2048 and try again.
Note: To retain maximum compatibility across all browsers do not use an RSA key size of over 2048 at this time!