I’m not entirely certain what you’re describing here, but as a rule Dynamesh wont update topology unless there’s something to update, for instance vertices have changes position, or you change a setting in the Dynamesh menu that requires an update, like Blur. If you make a single stroke on an object, it will retopologize when you re-mesh.
I have noticed that in some specific situations with multiple meshes in the same subtool, and the groups button is pressed, if you edit one object but not another, Dynamesh will only update the object that was edited, leaving the other unchanged. Sometimes a second re-mesh will update the other object. Otherwise un-press the Groups button to make sure everything is updated as one mesh.
Most situations in Dynamesh can be fixed by simple hitting Undo, and adjusting settings until you get the result you want. If for some reason this is not applicable to your situation and you want more mesh resolution, remember you can always subdivide the object. Just remember theres an upper limit to Dynamesh for detail, and extreme detail will begin to be lost.