Manifold 9.0.181.0 got into a state where selection in drawing windows was disabled.

(The tables are indexed.)

Ctrl-click on an object (with the default cursor) in the drawing window did nothing.

On the Edit menu, all the object selection options were greyed out.

I could select a row in a table (with Ctrl-click), and that row would be highlighted red, but on the corresponding drawing window, that object did not show red.

I closed Manifold, re-opened Manifold, and opened the map file, then selection on drawing windows worked fine.

What could cause this scenario? (I am NOT an experienced Manifold user.)

In case you have changes basic connections in the unterlaying structur - say you changed the name of the table and have corrected the propery of the dependent drawing you need to delete the drawing from the layers and readd it.

Do you really want to ruin economy only to save the planet?