Joomla Failed to start the session

same php version on both old and new server setups ?

quite a few google results if you search for "Error displaying the error page: Application Instantiation Error:Failed to start the session" as it's joomla specific

 

if it's igbinary, you can check by temp disabling the extension load line in igbinary.ini file

the command below lists all custom PHP extensions' ini file paths for extensions added by Centmin Mod specifically

Code (Text):

php --ini

find the igbinary.ini path file and edit it and comment out the extension load line and restart PHP-FPM service

example

Code (Text):

php --ini
Configuration File (php.ini) Path: /usr/local/lib
Loaded Configuration File: /usr/local/lib/php.ini
Scan for additional .ini files in: /etc/centminmod/php.d
Additional .ini files parsed: /etc/centminmod/php.d/a_customphp.ini,
/etc/centminmod/php.d/curlcainfo.ini,
/etc/centminmod/php.d/geoip.ini,
/etc/centminmod/php.d/igbinary.ini,
/etc/centminmod/php.d/imagick.ini,
/etc/centminmod/php.d/memcache.ini,
/etc/centminmod/php.d/memcached.ini,
/etc/centminmod/php.d/mongodb.ini,
/etc/centminmod/php.d/redis.ini,
/etc/centminmod/php.d/suhosin.ini

restart PHP

Code (Text):

service php-fpm restart

or with command shortcut

Code (Text):

fpmrestart

If that fixes it, you can try permanently disabling php igbinary install via creating persistent config file at /etc/centminmod/custom_config.inc and add to it

Code (Text):

IGBINARY_INSTALL='n'

then whenever in future you recompile or update PHP via centmin.sh menu option 5, php igbinary is not installed