So I assume you have the last update of ATUM. Please, now I have to ask you to deactivate all plugins except ATUM and woocommerce and check if the problem persists. This is to check if there is any incompatibility.
If this is still not working, please, I have to ask you to open a private ticket and provide us with your website credentials in order to take a look. Also, I have to ask you for permission to download a backup in case we need to make tests, as we have a very strict policy about not modifying anything in our users' live sites.
This is the link to open the private ticket: https://stockmanagementlabs.ticksy.com/