In templates/submit_templates/property_description_first.php replace

<input style=”float:left;” type=”checkbox” class=”form-control” value=”1″ id=”instant_booking” name=”instant_booking” <?php print $instant_booking; ?> >

with

<input checked style=”float:left;” type=”checkbox” class=”form-control” value=”1″ id=”instant_booking” name=”instant_booking” <?php print $instant_booking; ?> >

The “” from the code, need to be replaced manually in the pasted code or you can write manually the new code to make sure it will apply.