Similar issue here, but I ran into the guzzle error when updating Facebook Pixel to v2.2.1. Looks like that update changes the guzzle version which causes Simple Calendar to fail when loading the page.
Facebook Pixel v2.2.0 does work with Simple Calendar.
This was the error I found after the update:
Uncaught Error: Call to undefined method GuzzleHttp\Utils::chooseHandler() in /code/wp-content/plugins/google-calendar-events/vendor/guzzlehttp/guzzle/src/functions.php:61 Stack trace: #0 /code/wp-content/plugins/official-facebook-pixel/vendor/guzzlehttp/guzzle/src/HandlerStack.php(42): GuzzleHttp\choose_handler()