Compatible Junos versions for CSO 6.3.0
Junos Release 20.4R3-S5 and above or 22.2R3-S2 or 22.2R3-S4 or 22.2R3-S6 are compatible with Contrail Service Orchestration 6.3.0.
https://www.juniper.net/documentation/us/en/software/cso6.3.0/release-notes/cso-6.3.0-release-notes/cso-release-notes-6.3.0/topics/software-support/software-support.html