PHP limits post_max_size and upload_max_filesize are set to 50Mb for subscription at *Domains -> example.com -> PHP settings. Php configuration file "%plesk_dir%"\Additional\PleskPHP54\php.ini contains the following sets:
post_max_size = 20M upload_max_filesize = 20M
As a result, it is not possible to upload file which size is larger than 20Mb.
Mentioned PHP settings for the domain does not override Plesk settings in "%plesk_dir%"\Additional\
This is Plesk internal issue with id #PPPM-2898, which is planned to be fixed in future Plesk updates.
.user.inifile in DocumentRoot folder of the domain:
Specify the following settings in
post_max_size = 50M upload_max_filesize = 50M
Restart IIS to apply the settings above