The possible reasons are:
1. Typo or spaces (often at the beginning) in the license key. Use Copy/Paste method!
2. A wrong product has been chosen.
For example, MZpack Indicators and MZpack Indicators w Divergence are different products. Check what product you purchased previously. If you purchased one or more single indicators (not the whole package) choose MZpack Single Indicators from drop-down.
3. Your payed subscription period has ended
You must log in to the site with your purchase login to see Download/Installer link(s) in your account