Hello,
I can find no documentation at Viya 3.3 or 3.4 regarding a "sync" cas action or "sync" casl statement.
In my Viya 3.4 environment, the satement "sync asyncstatus;" is causing this error:
ERROR: The action 'sync' was not submitted.
ERROR: Operand is not a list
ERROR: sync asyncstatus ;
ERROR: ^
ERROR: Execution halted
But this code worked for you at Viya 3.3 ?