If you have a Drupal CMS installation version 1.0 (January 2025), you may have issues upgrading to the latest Drupal core (11.2). Neither automatic updates nor the "old fashioned" composer work.
You are not alone.
The reason for this behavior is that for 2 (automatic updates and project browser), versions included in Drupal CMS 1.0 are not compatible with Drupal core 11.2.
Here's a small trick to solve this version loop: tell composer to use the newer versions of contrib modules before asking to update the core:
composer require drupal/automatic_updates:^4 --no-update
composer require drupal/project_browser:^2.1 --no-update
and then update the core with recommended
composer update drupal/core* -W
If that won't work either, open your composer.json in any text editor, and replace version "1.0" with "^1.2" for all "drupal_cms_*" packages.
Have a great day