eBay has over the weekend switched off the 'large merchant services API' that Teapplix currently uses for mark orders as shipped. As a result orders you shipped over the weekend may not be marked as shipped.
Teapplix has implemented new eBay REST API. To migrate to this new REST API, you need to go to (new ui) integration/marketplaces --> and delete the eBay token and link eBay again.
New REST API token will have a 'Renew' button in Teapplix new ui. Old integration will not have a 'Renew' button, you should delete all such token and link again.
After link, you can sync orders and verify that orders are marked shipped successfully on eBay.
If you use PayPal integration to download your eBay orders, please note that this new REST API do not support PayPal integration anymore, and you must remove your PayPal integration. Otherwise you will get duplicate orders.
Also, the new REST API integration requires all 'variations' you sell has SKU setup and not just a title.