Today’s day quite a lot of users are using different solutions to keep their privacy on a good level. However, that means that when the page is loaded some content will never be loaded as they are being blocked by ad/trackers blockers.
So, if you’re using Google Tag Manager and add tags then everything that is being triggered there will not work when Google Tag Manager will be blocked.
For example, using Brave browser Google Tag Manager is blocked by default. See:
I’d recommend to check if you need to trigger anything inside Google Tag Manager and keep “widgets” outside of Google Tag Manager.
Update: seems Safari 14 protects privacy in a way that Google Tag Manager is able to load tags. See more in Understanding Safari’s New Privacy Report.