Question

I'm trying to save the changes I've made to the layers on a map I'm working on. 

I created a map with OpenStreetMap as my base map, played around with hiding some of the roads, hiding the labels of the suburbs/parks/rivers, hiding the visibility of some of the layers (like Points of Interest) and hit Save. 

But when I reloaded my map, my changes weren't saved!

Solution

The problem is that you were trying to update a map reference. What is that??

When ever you create a map from a base map, or if you add another map to your current map, that map will have this icon next to it: 

This indicates that it is a map reference. If there are any changes made to the original map (for instance if a new layer is added to OpenStreetMap or the styling changes), then those changes are reflected in any other map that references it.

However, because of the nature of referenced maps, you cannot save any changes to the referenced map.

How do you get around this?

Right click on your map and click "Convert to group"

You should now see a group icon on your map 

What this means is that you've taken a copy of the map and all its layers. You're now free to edit it to your heart's content, but none of the changes to the original map will be reflected in your new map.