Many things could stop working properly when the VCSA services stop working properly. Please see some scenarios below.
VCSA certs expired.
When the certs expire, 3rd party connections fail due to VC no longer being trusted. VCSA services eventually stop working and will fail to start.
Follow steps from "vCert - Scripted vCenter Expired Certificate Replacement" to use vCert tool to confirm VCSA certificate status and renew expired certs.