PS CC 2019 error/reinstall message

When the CC client show you thast you have updatres for version 20 and 21 it seems that you have installed both version on you computer. This matches also with the message that you should do an reinstall of PS 2019.

Try to deinstall both versions and then install the appropriate version again. If this doesn't help I would recommend a clean reinstallation by following the steps below: 

• uninstall everything cc including preferences, https://helpx.adobe.com/creative-cloud/help/uninstall-remove-app.html  
• then uninstall the cc desktop app, https://helpx.adobe.com/creative-cloud/help/uninstall-creative-cloud-desktop-app.html  
• clean your computer of cc files per http://www.adobe.com/support/contact/cscleanertool.html  
• restart your computer (don't skip this)  
• reinstall the cc desktop app, https://creative.adobe.com/products/creative-cloud.  

if you're unable to install the cc desktop app at this stage, use an administrator account (solution 4 here, https://helpx.adobe.com/creative-cloud/kb/creative-cloud-missing-damaged.html)  

use the desktop app to install your cc programs/trials