I am unable to update MacBook to macOS Monterey as Macintosh HD missing

User wrote " And when i press continue to update it says that macos monterey cannot be installed on ssd. "

UpGrading from macOS 10.15 Catalina would have required the Internal Drive to be formatted in the APFS / GUID Partition Map

So that would eliminate that as a possible issue and preventing the Installation of macOS 12 Monterey

So the next two question may become important

One, how much Empty Space is there on the Drive ?

Anything less that 50 GB would possible present this issue

Two, not often done but can be done.

Has the Original Apple Internal SSD Drive been replaced with an After Market Third Party SSD drive ?

That can pose an issue especially as it relates to upGrading to Monterey version 12.3.1 and above

In Disk Utility>View, select Show all Devices, highlight the top left entry.

Does it showt here?

Follow the advise from @BDAqua

If you what to Try >> Option-Command-R.

When you press and hold these three keys at startup, Recovery might offer the latest macOS that is compatible with your Mac

As you have addressed @BDAqua and I am still here

Below is Disk Utilities >> View >> Show all Devices

The Upper Most would be Apple SSD AP0256Z Media

I'm afraid you need to get an external drive & install to that.

Get an external drive...

https://eshop.macsales.com/shop/owc-express-1m2

https://eshop.macsales.com/shop/owc-envoy

https://eshop.macsales.com/shop/owc-envoy-pro-sx

https://eshop.macsales.com/item/OWC/ENVPMCA05/

Then boot into Restore Mode & install...

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

Follow the advise from @BDAqua - First

Just to add

In Finder >> Setting >> Show items on Desktop

Check mark " Hard disks "

Does the Macintosh Hard Drive appear on Desktop ?

It would look much like this

That is the >> Macintosh HD

So, it is there and not missing

Patience of Job 👍