I believe keywords do not sync.
Adobe recommends using the programs independently.
CC is a separate program and should be used as such
how can i make sure all keywords are sync from Adobe Lightroom Classic CC into Lightroom CC
MontyMontgomery is correct, keywords (and location data) do not sync between LR Classic and the cloud ecosystem. However, it is currently possible to effect a one way, one time transfer of your existing Classic keywords and location data in a specific image if you save metadata to XMP (Ctrl/Cmd+S) before you start syncing that image from Classic.
I stress the "currently" as I don't know if this capability is by design, or a bug, or simply a loophole, so I can't say if this one way transfer will continue following subsequent updates.
thank you for your feedback, how i wish adobe look into solving this. i understand both program work as independent, but it should have an option to import exisiting metadata.