Error: Peer's certificate or fingerprint wasn't verified fine.

Using thinos 9.3 on optiplex 3000 units, RDS broker deployment.  Updated the certificate from same source (sectigo) and began receiving this error on thin clients. Deploying the certificate with WMS resolved the issue ... But I'm confused why this time this was necessary. Previously we did not need to deploy the certificate to the thin clients upon renewal. Any ideas?