I did not see an 'Available' option. I selected 'configure' instead and managed to get a certificate.
Do a search for the EMM-mdm-cert.pdf document. A KB article is at https://kc.mcafee.com/corporate/index?page=content&id=KB70502&pmv=print
The openssl command line may give you some trouble if you are on a Windows environment:
openssl req -out CertificateSigningRequest.certSigningRequest -new -newkey rsa:2048 -subj /emailAddressfirstname.lastname@example.org/CN=”Company MDM Key”/C=US -nodes -keyout privateKey.key
Change 'CertificateSigningRequest.certSigningRequest' to be a filename ending in '.csr' - this is what you attach as part of the process. I also had errors with the Cygwin openssl implementation not liking the 'CN=”Company MDM Key”' component. I shortened it and removed the quotes to be just the one word, no spaces.
Hope this helps.