Welcome to the community!
Sorry to hear that only the buttons appear but not the icons. This could be due to a few reasons.
Have you enabled Font Awesome in the settings? Under the heading 'Import icon library'.
If so, my question is whether you are using a Cache plugin? Are you perhaps using WP-Rocket's Remove Unused CSS (Beta)?
This could be removing Font Awesome causing the icons to dissappear. If so, could you try and add this into the CSS safelist directly under Remove Unused CSS (Beta)?
Let me know if this helps.