Hi! Wow, this issue seems to seek and find Leonardos.
http://stuffics.com/ currently results in “origin is unreachable” from Cloudflare, so I can’t check what the specific symptom with your favicon is.
If it is HTTP 404 when attempting to fetch it, can you try the following safe and idempotent snippet on a Rails console? “Optimized” versions are derivatives of the original which will be untouched; these will just be regenerated.