Font Icons being hidden on header menu

I’m trying to add a phone number and a phone icon in the hedaer, but it hides it automatically. When customizing the page, here’s what I see: https://i.imgur.com/y204dbW.png

When publishing it and checking it out, here’s what happens: https://i.imgur.com/HgFjw35.png

It’s kinda urgent to fix this, client’s waiting.