App is working fine as long as all your customers are subscribed into VIES. If some of them are not, they can't proceed with their purchase which I believe is a strong limitation. They should just go ahead with VAT included, as simple as that
Hi the app description clearly says it validates VIES VAT IDs. Not sure why you installed Exemptify?
Applied for a demo, installed it but it did not work for me. In particular when wholesale customers were logged in. So I mailed the developer to see if there were known issues with wholesale apps. The reply was very rude and basicly said the app was perfect so it could not be. No effort at all into searching what it could be. It might be a good app if it works, but not paying for a customer service like that.