usb c hard drive not mounting on MBP 14" 2021 but works on Win 11 laptop??

What is the make & model of this external drive?

Check the System Profiler USB section to see how much power the drive needs versus how much the Mac is able to provide it. Just because the LED is lit does not mean the drive has enough power to actually operate.

Make sure to disconnect all other external devices in case one of them is causing a problem.

Connect the drive directly to the laptop.

Try booting into Safe Mode to see if that makes any difference with accessing the drive.

Has anything with the laptop, the drive, or other devices including OS & app updates coincided with this failure?

Which computer/OS was used to format the drive with exFAT?

Within Disk Utility click "View" and select "Show All Devices" to see whether the physical drive appears on the left pane of Disk Utility.

macOS is less forgiving than other operating systems when an issue is encountered with a drive whether a hardware issue or a file system issue.

Did you try running a file system check on the drive using your Windows computer? You may want to use the Windows computer to check the health of the external drive. You can use GSmartControl to retrieve the health report from the external drive and post the full report here. There is a portable version of GSmartControl so no installation is required....it can be run from the Downloads folder once it has been extracted from the archive. Within GSmartControl just double-click on the drive icon you want to inspect and select View/Show/Save report (I forget which it is, but it is easy to view & save it).

Format the drive as exFAT on the Windows box and try again with the Mac. I've been far more successful with exFAT created on Windows than Mac when the goal is to use on both.

If you see the exFAT drive on your Mac, erase it and choose the Apple format you want.

Any chance it could be this?

https://9to5mac.com/2022/06/06/macos-ventura-usb-security/

Having to give USB and Thunderbolt accessories approval to communicate with the computer is a fairly new form of operation for macOS – it appeared in Ventura – and probably not what most long-term users expect.