To confirm the issue is only related to the SSL certficate.
1. From safeguard client, asset tab, uncheck the "Verify SSL Certificate" option.
2. Run Test Connection again.
3. Install/enable the SSL certificate if this is required.
Verify SSL Certificate
Use this option to enable or disable SSLCertificate verification on the asset. When enabled, Safeguard for Privileged Passwords compares the signing authority of the certificate presented by the asset to the certificates in the Trusted Certificates store every time Safeguard for Privileged Passwords connects to the asset. Trust must be established for Safeguard for Privileged Passwords to manage the asset. NOTE: For Safeguard for Privileged Passwords to verify an SSL certificate, you must add the asset's signing authority certificate to the Trusted Certificates store.