I have just attempted today the 22nd of May to purchase again KJFK V2 and am still getting invalid coupon
If the site said the coupon is invalid, it means you are doing something wrong.
Are you SURE you are trying to purchase JFK V2 ( V2!! )
If you try to purchase JFK V1 and insert the Coupon code for the JKF V2 upgrade, it will still tell you the Coupon is invalid, even if you email was right, because that Coupon is only valid for a JFK V2 purchase.
Even if this might sound confusing, there are two JFK products available for sale, the old version can stil be purchased, both because it's the only version for FS9, and because we lowered the price too, so someone might want to get it anyway, to get some savings.
despite sending you via email as requested my proof of purchase for v1 on the 17th of May.
Are you getting problems with your email ? I replied to you on the same day, telling your email was correct.