I experienced a problem during an upgrade of Aria Operations as the self-signed certificate had expired a year ago. Unfortunately, I couldn't simply replace this on vRealize Suite Lifecycle Manager because Aria Operations would not import the new certificate.
The fix for me was to generate a new certificate from vRealize Suite Lifecycle Manager, fill in the relevant information and save. You can download this cert by clicking on the ellipses on the right of the certificate. Go to Aria Operations and manually import the cert. The communication between the vRealize Suite Lifecycle Manager and Aria Operations was working again.