MacBook Pro (Retina, 15-inch, Mid 2015) Monterey will not install

One has posted in High Sierra macOS 10.13 ok. The user profile is showing MacBook Pro 15″, macOS 11.6 which is Big Sur - ok.

To address the High Sierra aspect of this macOS Monterey is compatible with these computers

To address the Big Sur aspect Big Sur 11.6 is out dated and needs to be updated to Dec 13, 2021 release of 11.6.2 before attempting the Monterey upGrade.

Notation regarding Monterey >>

There are reports appearing on the ASC Forums regarding failed installation of Monterey on older Qualifying Apple Computers. In most cases this is related to having a NON Apple Original internal drive ?  

The EFI Boot ROM included in Monterey is verifying for Original Apple Drive and if not found , may Balk or fail to upgrade to Monterey. 

Reports indicate the EFI BOOT ROM is Required to Flash the Computer and is a  requirement for a Successful Monterey Installation.

If above is a case in point affecting this computer and it does Qualify for Monterey.

Flip out the After Market drive and replace with Apple Original Drive and run the Monterey Installer to that drive. The Flip Out the existing drive and replace with the After Market Drive and run the Monetreey Installer to this drive. It should install.

Welcome and Thank you too.

Do come back to the ASC Forums, in the future, if / or when additional question may arise