Parex Bridge Webhook issue

Hi, We use Parex Bridge to link WooCommerce to Xero but I am having problems with the syncronisation stopping between WooCommerce and Parex Bridge. Parex Bridge support have told me that it is because Webhooks for orders are getting disabled or the authorisation is being blocked. They say this is an issue with WooCommerce but I have no idea where to look to see if there is a setting that needs changing. Could you point me in the right direction? Thanks!