For those with Education accounts running the "paid content" error on download, could you please try again now (if you have a browser window open on Adobe Express, be sure to refresh it first)?
Sorry to hear you are running into this issue. This is most likely due to the use of some premium fonts in your file. For now, the immediate workaround is replace such fonts with free ones.
If you are not sure which fonts are paid/free and how to easily replace them, please reply here.