Impossible create backup of files witch dashboard tools for backup. Tool show message "Archived successfully!", but archive not created and debug get next error:

[13-Apr-2023 10:33:22 Europe/Vilnius] PHP Warning:  ZipArchive::close(): Can't open file: Permission denied in /var/www/html/domain.xx/oc-includes/osclass/utils.php on line 1413

Apache error log file:

[Thu Apr 13 10:33:22.799339 2023] [php7:warn] [pid 77931] [client 87.247.90.129:48552] PHP Warning:  ZipArchive::close(): Can't open file: Permission denied in /var/www/html/domain.xx/oc-includes/osclass/utils.php on line 1413, referer: https://www.domain.xx/oc-admin/index.php?page=tools&action=backup

Directory permision is 755
File perminsion is 644
Owner www-data:www-data
Osclass version: 8.1.1
PHP version: 7.4.3

What could be wrong?

Maybe you do not have correct permissions in root folder that does not allow create archive here?
That would be first what I would check

Permissions of root dir (/var/www/html/<domain>) is:
Access: (0755/drwxr-xr-x)  Uid: (   33/www-data)   Gid: (   33/www-data)

It seems to me that permissions of root dir are good.

Where else could there be a mistake?

Try to set 0755 chmod for all folders and subfolders.

nothing helps, I tried to make permissions 777 for all, 755 for dir and 644 for file, same error 

Last what comes to my mind is to test ZIP function manually on your site, that you create small script and try to run it, if it can zip.

The compression function in the terminal works, php-zip is installed. The reason remains unclear, but it seems to be related to OS and PHP. The situation was resolved when the migrated from VPS to hosting.

Interesting, there could be relation between chmod - zip - php, but some of these settings are even hidden and usually just hostiing can help to resolve.