A gps will sometime trigger on an obstruction or no-go by proximity, not on the actual track. For example, mine doesn't like an area on US-90 in north Florida, claiming there's a low clearance, while the actual low clearance is on a road a few hundred yards over.
I suspect yours is seeing Old US-127 and triggering a no-go, while you actually will travel on US-127 right alongside. Or it could perhaps be a weight restriction.
I looked using Google Earth and didn't see any obstruction and also saw several heavy trucks and large campers along the way. Looks like you may be going through a huge, perhaps private, sand mine.
-jbh-