Bank transfers take a while to be processed between the banks!
Your proof is one of initiating the transfer , but the actual transfer and vMix receiving it and ability to check that takes longer.
Your proof does help them what to look for , so maybe they are just waiting to see it on their account.

Also you don't mention any time frame your started the transfer or the emails, they are not living in the same timezone !

If it was bought via the main online store, then this is provided by a payment processing company called Fastspring, so I presume your payment would have been sent to them, and not to vMix directly. When Fastspring receive the payment they notify vMix to issue the licence, so if this is how you have purchased vMix I would suggest you start by contact Fastspring. vMix will probably not know anything about your purchase unless they have been notified by Fastspring (when the payment was received), so will be unable to help.

Of course if Fastspring say that they have received your payment and notified vMix, then maybe you should be contacting vMix to see if/where/when the licence was sent to you, but in my experience the licence email comes from Fastspring, not from vMix, so once again I suggest that contacting Fastspring is the best thing to do.