Input for social links not opening

I’m trying to add social icons to a theme’s Widgets area using the WordPress Widgets admin page, and this widget’s failing to open the text box to enter the URLs for the social media icons. I’ll click on, for example, the Facebook icon to insert my client’s facebook link, but no input box opens up for me to enter their URL in.

I tested the widget in Page Building and it works normally there, but not in the Widgets editor. Unfortunately inserting the social links using Page Builder is no good as I can’t access the right blocks on the page that the social icons need to be added to.

This is obviously a bug as I should be able to get full and normal functionality from anywhere in WordPress for this plugin.