Messages are not removed on request - OJS v. 3.1

Good morning,
OJS version (PHP 5.6.33, mysql 5.6.38) works correctly except for submission. If you try to delete an overdue message, the message "An unexpected error has occurred. Please reload the page and try again. "
I am removing part these messages directly in the database (field email_log) and the uploaded files are removed from the files folder, but this is not a good solution.
Any ideas ?

Please check your php error log and check in your browser Inspect element when this happens and report if there are some errors there.

Each message removal from Submissions (all active or archives) generates
this error php:
[Fri Feb 02 14:40:23.860861 2018] [access_compat:error] [pid 32102] [client] AH01797: client denied by server configuration:
/home/marekv01/domains/, referer:

Maybe I should modify the file question only in what place?
I logged in as an administrator and it seemed to me that I could also
delete incomplete Submissions ?

What is your role in OJS when you want to do that?

I’m an administrator, but the same error occurs when I’m an editor

Please check your and check did you set up everything in a right way concerning mails, envelope, scheduled tasks etc.