Rae from Shopify here.
Thanks for posting this question. I'm happy to help take a closer look into what's happening with the favicon on your theme.
Before we jump into some troubleshooting though, have you had a chance to double check your theme settings to confirm your favicon is set up correctly? I recommend doing this as a starting point by following these steps:
If your favicon is still not showing up after completing these steps, please reply back to me here with the following details:
I look forward to hearing back from you with this information and working on some further troubleshooting together!