You can contact the developer of your add-on at the address you will find in the marketplace.
How to find the email address or point of contact for that developer:
- Open the Marketplace
- Type the name of your addon in the search field
- Scroll down under the description until you see "Support Contact"
If you don't remember the name of your addon
- Select the category of your addon (for instance "aircraft")
- Click on "See all category"
- Then Show "Owned only"