Hey @elena_stanciu6519, Welcome to our Adobe Express Community!
Can you share the project URL via community DM so we can test it? Do you see any blank layers in the project?
Also, to save time, I'd suggest that as a workaround, you download the project as PNG or JPG and then convert it to PDF using the Adobe Express Quick action Convert to PDF tool, so your work doesn't get hampered.
Do let us know!
Best,
Amitej