[Plugin: Simple Popup Plugin] shows error

I have the same thing, and would really love to see if the developers know why this is happening. I just need a simple pop-up feature and I thought this was it – but I need it to work in PHP theme files.

One thing, I figured out that the PHP code they show is not quite right. See the problem below:

<?php echo do_shortcode('[popup url="https://website.com/file.html']Click to view[/popup]'); ?>

The end of the URL should be a quote to match the front – but instead it is an apostrophe. The URL you want to point to should be encased between quotation marks. I noticed that when changing this, I no longer got an error but I still don’t get the darn thing to work.

??