I bought the Supporters version but the advanced features are still blocked. What can it do?

This happens because you are still using the Community version even if you have purchased the Supporters version.

You can check this in the info section:

If you're using the Supporters Edition you should see the suffix SE beside the version number:

Instead, if you are still using the Community Edition you see the suffix CE beside the version number:

In conclusion: bibisco Supporters Edition and bibisco Community Edition are different applications, so you have to download, unzip and launch Supporters Edition as described in the link here: How to upgrade from Community to Supporters Edition.

In particular, pay attention at the name of the zip: bibisco-win32-x64-2.X.Y-SE.zip is the zip for Supporters Edition, bibisco-win32-x64-2.X.Y-CE.zip is the zip for Community Edition.