Reach out to Support to enable a required setting to keep your FBM quantities up to date.
Amazon made changes in October 2020, which may impact quantity updates for your FBM items if you're in this program. They now require additional information on Fulfillment Type be sent to Amazon in order to be able to update quantities correctly. SellerActive has a setting that will allow our system to send this required Fulfillment Type information to Amazon and continue to update your FBA and FBM quantities.
Please reach out to SellerActive to inform us if you're in this program and we'll turn this setting on for your account (Please verify all of your FBM quantities are correct prior to reaching out). If it is not on, SellerActive may not be able to update your FBM quantities. Please see this article for more information on this setting, which will automatically flip fulfillment types between FBA and FBM as your available inventory changes.