The Pro uses Font Awesome, font icons to show those and the problem of square icons show that the font is not detected most probably because your server blocks it.
Please follow the steps mentioned in this article to fix the problem.
You may have to contact your hosting service provider for this.
Also, I suggest that you follow the steps below:
- Ensure everything is up to date according to our version compatibility list here. Please follow the best practices when updating your theme and plugins. Click here for more information.
- Test for a plugin conflict. You can do this by deactivating all third-party plugins, and see if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.