it is strange since there was no changes in the settings between 6.0 and 6.1.. the only change was between 5.4 and 6.0. Can you confirm it was working in 6.0 and not in 5.4 I strongly believe that it is possible the upgrade patch from 5.4 to 6.0 to have not been executed which may cause this issue. But from 6.0 to 6.1.x there was no upgrades related to that.
Can you please also try to open /Sitefinity/ecommerce/TaxSettings
and let me know is it working ? just to make sure that just the link is broken not the page itself .
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