You need to check how your pixel works with the default theme first. Does it work ok? Could you provide screenshots that with the default Storefront theme it works?
Pixel code should be added in head https://prnt.sc/101ubrj
But you added it to footer static block and also installed the plugin.
I moved Pixel code to head https://prnt.sc/101ug25
Do you need both: code and plugin? Because I think that you need to use either code or plugin. And using both gives you th mentioned error.
