Upgrading from php 7.2 to 7.3 causes site to not start

[axiomcs]

Website is hosted on a physical private server running Windows Server 2012 with Joomla 3.9.23. Server is using Xampp. Uninstalled Xampp 7.2 and deleted folder and contents of c:\xampp. Installed Xampp 7.3. Created new db using phpmyadmin and added a password to the root user. Imported db from working 7.2 version.

Getting this error/warning in browser at 127.0.0.1:
"Warning: session start(): Failed to read session data: user: c:\xampp\tmp in c:\users\username\website\libraries\joomla\session\handler\native.php on line 260
Error: Failed to start application: Failed to start session"

Changed in configuration.php all references of localhost to 127.0.0.1.

Need help with getting site to start successfully. Don't know what else to try. All searching I have done seems to point to changing localhost to 127.0.0.1 in the configuration.php file at the site's root folder..

[Globulopolis]

PHP do not create folders automatically. Check sys_temp_dir option in php.ini and check if that folder is really exists.

[axiomcs]

In the php.ini file it shows this:

;sys_temp_dir = "/tmp"

There is a folder c:\xampp\tmp, but no c:\tmp folder.

[Nobbie]

Ok and what does that mean for you?

[axiomcs]

Uncomment it and change it to c:\xampp\tmp?

Which I did and got the same result.

[Nobbie]

It looks as if you should have backuped and restored c:/xampp/tmp as well, due to the error message Joomla fails zo load session data for user from that folder.

You should ask in a Joomla support forum how to fix that.