: complaints: wp_session_manager_start_session() and other errors too

[dil_bert]

topic of this post: complaints: wp_session_manager_start_session()  and other errors too 

after having reworked on the server-hardware i set back the server live some weeks later. now i have errors see below. 

guess that this has to do with the newer releases... 

see the <strong>history of wp versions. </strong>

5.5.1    23. September 2020    zip
5.5    1. September 2020    zip

5.4-branch
5.4.2    2. August 2020    zip

well i have running the version 5.4.2

see the errors and complaining 

site1:

Fatal error: Uncaught Exception:
	`Cannot open source device in /sites/www.mysite.de/wp-content/plugins/participants-database/vendor/wp-session-manager/wp-session-manager.php:46 
Stack trace: #0 /sites/www.mysite.de/wp-content/plugins/participants-database/vendor/wp-session-manager/wp-session-manager.php(46): 
session_start() 
#1 /sites/www.mysite.de/wp-includes/class-wp-hook.php(289): wp_session_manager_start_session() 
#2 /sites/www.mysite.de/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array) 
#3 /sites/www.mysite.de/wp-includes/plugin.php(478): WP_Hook->do_action(Array) 
#4 /sites/www.mysite.de/wp-settings.php(403): do_action('plugins_loaded') 
#5 /sites/www.mysite.de/wp-config.php(97): require_once('/sites/www.mysite....') 
#6 /sites/www.mysite.de/wp-load.php(37): require_once('/sites/www.mysite....') 
#7 /sites/www.mysite.de/wp-blog-header.php(13): require_once('/sites/www.mysite....') 
#8 /sites/www.mysite.de/index.php(17): require('/sites/www.mysite...') 
#9 {main} Next  Error: Failed to create session ID: user (path: /tmp/) in 
in /sites/www.mysite.de/wp-content/plugins/participants-database/vendor/wp-session-manager/wp-session-manager.php on line 46
There has been a critical error on your website.
	Learn more about debugging in WordPress.

site 2:

There has been a critical error on your website.
Learn more about debugging in WordPress.

Well - what do you suggest: should i first upgrade the versions to the newest version!? 
again - we did not change any thing in the software of the server - we only changed the hardware...

look forward to hear  from you 

regards