To make sure your connection to a Vendor's system is working properly, can perform a connection Health Check.
NOTE: Make sure that you are operating at the right Vendor/Warehouse beforehand.
To perform a connection Health Check, you will have to:
1. Click Channels under Sales Channels
2. Click Health Check for the Sales Channel you'd like to check
3. Wait until the process completes; if it completes successfully you will see a confirmation, if not, you will see an error message and should verify if the URL is still active or has permission issues