when trying to add tag
how do I fix it
Amazon no longer supported. See [2017-06-22] in the changelog.
Use another WSS.
This has been explained a number of times....please see do a search of the forums under Amazon and you will find multiple posts indicating that Amazon have terminated the accounts that were associated with this function which has removed the ability to use these and therefore they have been removed from future versions.
The reason I suggest doing a search rather than giving you a direct link is that there were some suggestions of work arounds in some of the threads but if they do actually work you will have to find out for yourself.