Mac Pro 2019 not booting

Mac Pro with Xeon processor feature Error Correcting Code RAM modules. If ANY error, correctable or not, is detected during the power-on self test, those slots will be declared 'empty' and macOS will not consider using them until next restart.

Uncorrectable errors that occur in the running system cause a kernel panic, machine check, with a fairly distinctive crash report. They also leave the red LED next to the failing module(s) lit until the power is interrupted. Unfortunately on the 2019 model, the handle is power-interlocked, so you can't remove the case to check, you have to look in the grilles.

Internet Recovery does not require anything from any drive. It creates about 25 RAM disks to hold temporary items.

If you cam't boot to Internet recovery, you have a serious hardware problem beyond the drive problem. Diagnostics might tell you more.

The initial "chime" sound is generated in software when your Mac passes the Power-On Self Test. If the chime occurs and/or startup continues, your Mac is working. The blank gray screen should light up. Then on to the disk Drive.

Accessing the Boot drive:

The solid Apple is not in the Mac's ROM at Cold start. The Apple logo can only appear when it is fetched in the first "blob" of software loaded from a 'magic' place on the boot drive, or re-run after a Restart. Then a whole lot of stuff is initialized, and the progress Bar moves part way across. After a cold start, seeing the solid Apple appear says your drive is not completely dead.

Mounting the Boot drive:

The next step requires a lot of files by name, so the File System is initialized, and the Boot Drive is Mounted. If the drive directory is damaged, the drive can not be Mounted, so your Mac begins one pass of Disk Utility Repair. This will take an additional about five minutes. During this process, the progress bar may be extended, and will grow by an additional amount not seen on a routine startup.

at the end of that process (which should not take more than about five minutes), it will attempt to Mount the drive again:

-- if the drive Mounts, boot-up continues.

-- if the drive cannot be Mounted, your Mac can do nothing more, so it powers off.

-- if the process stalls, this may indicate you have Bad Blocks on your Rotating Magnetic Boot drive (if so equipped). The re-reading of Bad blocks can take a very long time (on the order of a quarter minute for each Bad Block).

Expected behavior if the Hard drive is corrupted, especially in the area of the Directory, which will keep it from Mounting.

you can try booting to Recovery and running Disk Utility repair, but you may be looking at a MacOs re-install -- which of course requires that the drive can be mounted first.

¿what is the date of your most recent backup, and by what method?

Diagnostics loads across the Internet as well, so it takes the same quarter hour that Internet recovery takes to get going... but you should see the spinning Globe to entertain you while it loads.

If you used ANY Windows-native software that inspects or modifies the Partition Map, it has a reputation for clobbering the Partition Map, wiping out the MacOS partition. Windows is not a pleasant guest.