Let's enrypt doesn't create cert to secure plesk itself

Hi,

CentOS 7, Pleask 12.5#43

all other server with identical config: working perfect; but one server exhibits the following:

log into plesk as admin, go to subscription matching the servers hostname [server4.owncompany.com], go to let's encrypt, renew cert with "use to secure plesk" ticked.
The cert for the domain [non 8443] is renewed, but the cert for securing plesk is not created. (doesn't show as an available cert under tools&settings / SSL).

Anyone in the forum with indepth...

Let's enrypt doesn't create cert to secure plesk itself