I bought an item using regular lisence, but my customer ask to change to extended. How to do this? How pay extra? Thanks
If you really need extended license, I would talk/contact the author of the item and ask him when I buy a new extended licenses, to give me a refund for the regular license which you have already bought.
That can be the easiest and the fast way because there is no option (by default) just to “pay extra” and to get the extended version.
Of course, you can try to contact Envato Help about this situation and maybe they give you a option to “pay extra” - but that can take some time.