Image upload

Hi, I’ve got a problem uploading images within the aio calendar 1.9
Everything works fine for me as the admin, but when visitors no matter what permission they have, the “add files/images” is missing and when uploading article images the message ” http error ” shows up.
I asked Timely already, but I think it could also be a wp problem ???
Many thanks in advance for helping.
Best regards
Elisabeth
https://www.elisabethrae.at