I have an issue with onSelectionChange function - it just stopped working for me.
function onSelectionChange(e) {
  // Set background to red if a single empty cell is selected.
  var range = e.range;
  if(range.getNumRows() === 1 
      && range.getNumColumns() === 1 
      && range.getCell(1, 1).getValue() === "") {
    range.setBackground("red");
  }
}
Whatever do I put here it is not running. Even if it is just msgBox or something else. In Logger just after it triggers, it says "runtime 0 seconds" and I receive error "Maximum execution time exceeded". What's going on?