pixel not added to page

We have connected our store to FB with this plugin. It has worked for a long time. But from about a month ago, we started to lose pixel traffic, from our recent troubleshoot, it seems when an anonymous visitor accesses our site, e.g.

view-source:https://www.yoyoshop123.com/shop/

There is no pixel integrated to the page source at all. However, when logged in as admin, the pixel code is always present.