This error is coming from Amazon. Your account has been blocked and is not permitting us access. You are likely getting a lengthy error message, something like this - but specific to your Merchant ID (where the XXXXX is below):
Amazon message: encryptedMerchantCustomerId: XXXXX is unable to inbound. Reason: Seller is blocked by the AndonCordManager. - This operation may be partially successful, Please check the status. Reason: encryptedMerchantCustomerId: XXXXX is unable to inbound. Reason: Seller is blocked by the AndonCordManager.Request Id: YYYYYY
Issues can focus on physical and functional defects or inconsistency with the product page description. For instance, the physical item lacks a feature that was listed on the product page or its coloring is different.
Check your shipments or inbound performance summary. There might be an issue there (such as sending in an overweight box) and you'll need to acknowledge it either on the summary page or shipment page before Amazon will let you inbound again.
If you don't seeing anything there, you can also try to replenish an affected ASIN already in your Inventory directly through Seller Central. You'll most likely experience similar issues that a Seller Support agent should be able to see and address if you contact them.
Once the issue has been acknowledged and Amazon clears this error from the MWS API we use to communicate with them, you'll be able to list again.
If the above does not resolve this, you will need to contact Seller Central support and give them the text of the error message you are getting.
Please let me know if you need anything further.