In order to project objects onto a grid, at least one grid object has to be selected, as well as the objects which are to be converted to this grid surface. If you select at least one object and exactly one grid object, then you can project the vector graphic object onto this grid.
If the projected object is a group, there is no need to dissolve the group. It will remain as a group when converted with the grid object. To project text, line, or scan area frames onto the grid, then you must firstly convert these frame objects to vector objects.