Apple won't accept Renewal Certificate

I upload the Prey “certificate.pem” to Apple, but get an error…
Here’s the error code I get:
“Invalid Certificate Signing Request
The Certificate Signing Request you entered appears to be invalid. Make sure that request file uploaded is in the correct format and not empty.”

I am having the same problem with my Mac running OS 11.2.1. I tried a couple months ago and gave up. My certificate expires in 14 days, and there doesn’t seem to be anything I can do about it. Did you ever get it to work?