When adding a sales tax to the sandbox I get the error attached. No more information given.
Application ID: sandbox-sq0idb-YdtqEeA28cXebiircwmRuA
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The tax was correctly created right? That error is above the tax and is a field for an unsupported object in sandbox. 
Hi Bryan,
While the tax does show up in the list of available taxes something is wrong with it. When trying to import the catalog used in production the import feature states that an item is missing for the “Sales Tax” header almost as if the import tool can’t see that the tax exists. I’ve included the application ID can you take a look?
I see that you were able to resolve this by adding the reporting category.