Can you show us a screenshot of the automations that you set up?
In most cases in SmartThings Classic you would need two automations to keep the switches in sync, one where A is the trigger and one where B is the trigger. I don’t think that’s true if you are using the new “smartthings (Samsung connect)” mobile app, but to be honest I’m not sure. That has a different rules engine.
Most people would not use direct association, because if you use direct association the hub will not be informed when the switches change status. That’s pretty much the definition of direct association, that it bypasses the hub.
But if you do want to use direct association, you can set it up by using the zwave tweaker DTH (code, not a device).
But again, if you do it that way, you may not be able to use physical presses to trigger automations because the hub won’t necessarily know the switch was activated.