I have the same issue. the problem was in the module:
Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: You have requested a non-existent service "colorbox.attachment";.
The module mantainer do not add colorbox to dependencies.
So you just to need to install and enable Colorbox module.
Answer from Romix on Stack Exchange8 - Video Embed Field with Magnific Popup - Drupal Answers
Insert images and use Magnific Popups styling? | Drupal.org
Magnific popup module works for me, but doesn't display how I want
Drupal - magnific popup only works when logged in - Stack Overflow
https://www.drupal.org/project/magnific_popup
Hi everyone. I am trying to use the module magnific popup. I managed to get it working fine, however I have one issue I am wondering if can be fixed. When you are on the page it shows all the individual images as a gallery you can even pick their size, then you click in to an image and it popups a larger one that you can then scroll left and right.
My issue is the thumbnails of those images appear vertically having a breakline after each one. I was wondering if they could go horizontally side by side. I feel like this is a much more common way for galleries to be shown and it seems odd it would just drop them one below the other. Is there anyway to make them on the same line? Thanks.