A mandatory locational attribute is missing

This means that there is an object that is not completely defined. We do not want those to be shared to the server.

An error message about this can come during sharing or after a "Validation". There should also be a line in the process window with a red triangle in front for all the objects that have errors.

Double click on the first such line in the process window, making the object selected. Now look in Properties to what the object is and to which task it belongs. Fix it.

After going through all suspected objects, you should be able to share.