Is BIOS setup as "legacy"?  It needs to be UEFI to enable TPM.  Also, if its setup as legacy and you want to convert to UEFI the drive must be reformatted to GPT.   
[IMAGE]                           I'm trying to set up my 2019 Inspiron 7777 to be ready to upgrade to Windows 11. My goofy BIOS set-up won't let me do anything with the TPM settings, which I need to get Window 11. I'm fairly sure from Dell's website that this PC came with TPM 2.0 installed, so how do I enable it! The TPM toggle is "greyed out" (I know it's really black instead of blue but I don't want to say "blacked out"). I can't figure out what BIOS' problem is.
Bios > Security > TPM toggle not accessible Inspiron 7777