Hey @DanielSP, I got a response from Gumroad support team. It looks like a known issue. However, they have provided me with few workarounds.
- Use a different browser, or
- Use a browser in incognito mode, or
- Use a different email address at checkout, so you can then reassign the purchase of your first email address you have used.
Try any one of these and let me know if it worked for you.
If it doesn’t, please wait for few more days till I make it available in other marketplace as well. I am just in the process of getting few more features (to make it more or less a feature-complete) before I publish it in BlenderMarket and et. al.