Some of that may depend on your LMS course settings, or maybe your course didn’t refresh when you republished at the same address location? (I think without that option it might start the user back at the beginning, but I could be wrong).
You could always track the progress of the user through the course, and have a button in your navigation that will take the user back to either the last page they completed, or to the furthest point in the course they progressed to? Maybe that button only shows up if the user starts back on the first page? Or even an action that shows a pop-up on a page when they open a course for the second time (or more) that will give them the option in your own dialog box to return to the page they left off, or the action could just immediately take them to the last page they were on (again, based on you tracking them through the course with a variable or status indicator).