Insert Category doesn't work?

I’m trying out the free version of Download Manager and I want to use the shortcode method of inserting a category of downloads. My shortcode was inserted using the TinyMCE button add-on. It looks like this:

[wpdm_category id=”angular-rate-sensor,” cols=”1″ toolbar=0 item_per_page=10 template=”link-template-button”]

But the page tab just says “Loading” for a long time and then I get a 504 server error.

I’ve tried disabling all my plugins but that doesn’t change anything.

Can you help?

https://wordpress.org/plugins/download-manager/