Icons font awesome lost after upgrading to 2.3

[PabloC]

As you can see in the image attached, my icons have disappeared from my forum (default style). I have read this https://xenforo.com/community/threads/boosting-performance-in-xenforo-2-3.216767/#post-1648280, and it looks like it talks about my issue, but I don't know how to correct it, and where (which templates) to edit.
Could anyone guide me?
Thanks!!
Icons font awesome lost after upgrading to 2.3

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