Hi,
Windows 10/11 Feature upgrades are automatically pushed via Windows Update if the system is supported. Please run the PC Health Check app to see if the system is compatible with the latest Windows 11 version (i.e., 26H2):
Download https://aka.ms/GetPCHealthCheckApp
Run the PC Health Check app, and click "Check now."
Click "See all results."
Post a screenshot of that dialog.