I have an Apple Mac Pro (late 2013) and it doesn't update to the latest MacOS Monterey, any reason why?

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The macOS Monterey install requires the latest firmware to be installed on your Mac Pro. Like myself, some have upgraded internal SSD drive to a non-Mac SSD. Because it is not OEM Apple SSD, the current firmware cannot be installed. Thus Monterey cannot be installed.

Does anyone have a work around as to how to install the firmware upgrade to an internal non-Mac SSD?

Re-install an original Apple SSD drive.

Re-install 10.13.6 to get a later firmware with a completely different numbering system installed on the Mac (it is not installed on the DRIVE, it goes into private store on the processor card).

then install Mojave, atleast 10.14.4 to get free of the Apple SSD drive requirement

then install MacOS Big Sur, at least 11.1 to get version 426.0.0.0 version

ref:

http://blog.greggant.com/posts/2019/05/07/the-definitive-mac-pro-2013-trashcan-guide.html#tfirmware

.

It is qualified if you have enough disk space, like 50GB free.

What is the exact wording of the error message?

I have a mac pro late 2013 that I replaced the sd drive. It will not install after download and just trying to install it made the mail app unloadable.