I have a 2TB PRO and get those speeds if I use a different cable other than the one supplied. If its not a 10K capable cable I get 45MB/s with the right one I get 1080MB/s. So make sure its the original cable and its in good condition.
Also I would change the device properties in Window Device Manager for ‘Better Performance’ and ‘Enable Write Cache’. Not your issue, but helps speed things up a little.