Invalid certificate (CSR)

I generate .certSigningRequest file via Keychain Access (Keychain Access -> Certificate Assistant -> Request a Certificate From a Certificate Authority..., I fill in my mail and I save it to disk).

When I log into Apple developer account and try to generate Certificate with it I get message: "Invalid CSR - Invalid Certificate"

I did this number of times previously with my previous Mac but it is not working on my new system.

What am I doing wrong? I have followed exact steps https://help.apple.com/developer-account/#/devbfa00fef7

I think this is a Apple error. you just need to simply refresh the website again and again or need to use another browser.