That icon suggest broken image/resource or a link to it.
In Google Chrome console on network tab (resources) I see the error:
Blocked - reason: Mixed content
You are trying to load HTTP resource over HTTPS:
Regarding Mixed Content, kindly I suggest to check below articles:
Could it be due to your SSL settings at Cloudflare dashboard for your domain?
Can you check what kind of an SSL option have you got enabled at SSL/TLS tab (Flexible SSL, Full, Strict)?
Therefore, I have tried and do not have and do not see a broken image error in Mozilla Firefox.