Social Media Icons not showing when programmed through theme

I have installed the WordPress theme “Tracks” which has integrated social media icons (that one can edit under Appearance>Customize>Social Media Icons). When I view my website as an admin (meaning I click “view website” from the dashboard after logging in) I can perfectly see the icons in my header and all the ones in my footer. When I open a new tab or access my website without being logged into WordPress, then the icons are replaced by empty rectangles. Nonetheless, if one clicks on the rectangles, the link still works.
These icons are not in the “widgets” category (unlike the ones in my footer – except for “Soundcloud” which displays the same problem as the other, since I integrated it through the theme customization). I do not want to just use the widget for my social media as it does not contain “Soundcloud”.
Please help.
Here’s my website: https://www.beatriceverzier.com

PS: There is also a weird white ring in the background that one can see when at the bottom of the page (or not if you only see rectangles as for the social media icons) – what is that?