After changing the Kvantum theme of your KDE system, you may encounter issues with KDE software not opening. Here are some steps to troubleshoot the problem:
Try resetting the Kvantum theme to the default settings.
Ensure that your KDE software and Kvantum theme are up to date.
Clear the cache of your KDE applications.
If the issue persists, consider reinstalling the Kvantum theme.
Review system logs for any error messages related to KDE applications.
If none of the above solutions work, consider reaching out to the KDE community for assistance.