I would think that the cable that came with the monitor should be fine. I do however see that you have 2 monitors connected. I am wondering if maybe, that is the issue. For the sake of trouble shooting your issue. Try disconnecting 1 monitor at a time then rebooting the machine, then see if it allows you to enable freesync on your freesync monitor. Are both of your monitors freesync capable, if not, that might be what is going on. If that is not an issue it can only be that freesync just isn't enabled in the monitor. Have you thoroughly checked all sub menus on the monitor. You typically have to enable freesync. It's not usually on by default.
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