Hello!

If you import menu field from Account Menu then field `addon` also should be copied from the source to your new Toolbar menu. Check please in database if your new menu item in sys_menu_items table for messenger has empty `addon` filed and if so then put into it this value

a:2:{s:6:"module";s:12:"bx_messenger";s:6:"method";s:20:"get_updated_lots_num";}

then notifications should work fine for messenger icon.