Great plugin! A little customisation help needed

I see lots of negative threads posted here about this plugin, yet very little good or even constructive feedback. So, here is mine- I’ve been using this plugin since as long as I can remember, & Never had any problems with it whatsoever. It’s brilliant. I use it when I’m developing customers sites, and even when I hand the site over to the client, I leave the plugin turned on so they can add content/ products to the site and view them on the front end, while non-admins/ editors still see the splash screen. It’s helped me out numerous times.

Now, I’m looking to get a bit more from this wonderful plugin- Rather than just display the boring, plain ‘Maintenance’ page, I’ve recently started creating a 503.php file for my themes, with some styling to match the site/ brand. However, I really miss the countdown.

Of course, if I could add the countdown to the 503 page – I would be a very happy man.

I tried to add this in the 503 page:

<?php echo do_shortcode('[until]'); ?>

…but it doesn’t seem to work.

Any advice/ suggestions? Would really love to get this working