Update to Win 11 says tpm 2.0 not found, but boot menu says it is present

My Lenovo ThinkPad X1 Carbon Gen 8 (20U9) 14″ laptop will not update to Windows 11: it says TPM 2.0 not found. I checked in the boot menu and it says TPM 2.0 is installed and active. I checked on the Lenovo website and it says that this computer has TPM 2.0. I’d appreciate any suggestions on how to resolve this.