Hi @gabrieldelpech
Thank you for creating this thread and apologies for not responding sooner.
The plugin uses gtag.js for tracking, also it supports only the standard woocomerce implementation.
As you are using GTM for tracking could also impact the gtag.js script (added by the plugin) could result in non-tracking.
The add to cart button should use a default woocommerce template hooks where the plugin will be able to track the events if any other being used could be a reason for non-tracking of cart events.