Failed opening required ‘/var/www/vhosts/mautic/app/…/vendor/autoload.php’ (include_path=’.:/opt/plesk/php/7.2/share/pear’) in /var/www/vhosts/mautic/app/autoload.php on line 15\n’

Your software
My Mautic version is:2.16
My PHP version is:7.3

Your problem
My problem is: 500 error

These errors are showing in the log:
Got error ‘PHP message: PHP Warning: require(/var/www/vhosts/techphenomenon.com/hub.techphenomenon.com/app/…/vendor/autoload.php): failed to open stream: No such file or directory in /var/www/vhosts/Mautic/app/autoload.php on line 15\nPHP message: PHP Warning: require(/var/www/vhosts/mautic/app/…/vendor/autoload.php): failed to open stream: No such file or directory in /var/www/vhosts/mautic/app/autoload.php on line 15\nPHP message: PHP Fatal error: require(): Failed opening required ‘/var/www/vhosts/mautic/app/…/vendor/autoload.php’ (include_path=’.:/opt/plesk/php/7.2/share/pear’) in /var/www/vhosts/mautic/app/autoload.php on line 15\n’
Steps I have tried to fix the problem: cleared cache - fresh mautic install

Hi there,

It isn’t clear when this error occurs - is it when you try to open Mautic?

Did you update at command line or via the UI to 2.16, or was it a fresh installation?

Was the update/install successful or were there any problems?

This error occurs when attempting to access the mautic dashboard.
In an attempt to correct this error I deleted original mautic files, unzipped a fresh download of 2.16 and copied over my local.php to app/config
Same error when I attempt to run any ssh commands:
PHP Warning: require(/var/www/vhosts/Mautic-Install/app/…/vendor/autoload.php): failed to open stream: No such file or directory in /var/www/vhosts/Mautic-Install/app/autoload.php on line 15

and:

PHP Fatal error: require(): Failed opening required ‘/var/www/vhosts/Mautic-Install/app/…/vendor/autoload.php’ (include_path=’.:/usr/share/pear:/usr/share/php’) in /var/www/vhosts/Mautic-Install/app/autoload.php on line 15

Fixed this issue with following steps:
Save copy of local.php from app/config directory
Delete all mautic files - remember to save media folder and any custom themes
upload and unzip version 2.16 downloaded from mautic in directory (not the mautic-staging zip on github)
copy local.php to config directory