I do wish these error messages were a little more informative, pointing
out where you made a mistake, but I am so glad it was something so
simple. Does it actually not know what the problem is? Rather than
saying "you put it in the wrong place" it says "the map item is not
valid", which makes me assume a syntax error rather than a command
hierarchy error.
(My favourite error is the one where I forget to click on some survey
stations when defining a scrap, and it tells me "this map is too large,
and you need to pick a smaller scale". Or the one where I click on a
station that was already defined in another scrap, and it fails to put
the right -name in the options - or it just picks the "next" station
number which was not the right one. Same error message. Or some random
code dumps about it failing to find the largest coordinate when closing
lines. These messages are ... "fun".)