The APP is well done, just doesn't work. I think they are still in BETA and I saw a lot of bugs with the sync. For instance there is limitation of the quantity of characters your SKUs can have (30). When an error is detected there no way to correct it and is not going to sync with Essentials anymore.
We're sorry to see you have had a negative experience Strumenti Tattici. Our support team has tried to reach out and help sort out the limitation you're experiencing. OneSaas does not have any SKU limitations on characters but respect that MYOB have a 30 character limit on SKU. Please reach out to firstname.lastname@example.org if you have any further questions and we'll be happy to help you out.