you need to ensure the value is present and not overwritten, i had to manually update the field every time (after removing the disable attribute) to make it work, as each AJAX action reset the value the previous ca values (that comes from ovirt).

IMHO overwriting the cert when you click on Load datacenters is broken by design. We should only set it when the field is empty (the initial setup) and add an extra button to explicitly fetch the certificate when it is already present.