Trying to import changed tax rates with Magento 220.127.116.11, and it's not working. I get no error message - it tells me "The tax rate has been imported." - but all the old tax rates are still there, and not replaced by the new tax rates.
I've tried a number of different variations in formatting, and the weird thing is that it has worked couple of times - so now 6 (of ~2500) zip codes are updated. But the files don't seem to have obvious formatting differences. And this process, in general, is something I've done before many times, without issue.
So - I'd love suggestions for what else to try, or alternative ways to update tax rates by zip code. We do not have a large volume on our store, so commercial solutions are probably not useful.