Uploaded documents are not visible in the Submissions + HTTP error


We have just installed OJS to http://www.langedutech.com/letjournal/index.php/let and launched our new journal. However, neither users nor the editors/journal administrator can see the uploaded documents. Submissions are not visible although we can see them in the folders of the hosting service.
Additionally, when the editors try to upload a document we see HTTP error.

How can we solve the problem?

Authors uploading their documents (but they are not visible)

After document submission
after doc upload

No files
no file

Editor or Administrator trying to upload the document (but error message)
http error

Problems fixed after updating PHP to 7.3
:smile: :sweat_smile: :+1:t3: