I used the jetson-nano-jp461-sd-card-image, which is the one that was given recommended for this version.
After I cleared it out and I tried to flash a different image, the JP513-orin-nano-sd-card-image_b29, and the processor would turn on and then turn back off.
Then after I cleared it out again and flashed the original SD image from the beginning.
The L4T Configuration > OS chain A status is Normal.
Be careful to use the correct software release. This particular forum is for the original (and much older) Jetson Nano. The Jetson Orin Nano is much newer and has a different set of releases it will work with.
FYI, the L4T release is just Ubuntu plus NVIDIA drivers. JetPack/SDK Manager is just a front end to the flash software that runs on the Linux PC, of which its goal is to install L4T to the Jetson. Is this truly an Orin Nano? If so, then you can use L4T R35.x or R36.x (which corresponds to JetPack 5.x or 6.x). If you pick either an L4T release or a JetPack release, then you are more or less doing the same thing (except JetPack has an option to see older L4T releases). I suggest you go the URL for L4T releases: https://developer.nvidia.com/linux-tegra
Get the latest version of L4T for your release. L4T R32.x, from JetPack 4.x, is incompatible with Orin. L4T R35.x is well tested. R36.x is fairly well tested also, but some of the concepts have changed, e.g., it uses mainline kernel instead of one patched for use on Jetsons. You will find documents related to the specific release on that L4T URL, along with a link to JetPack/SDK Manager. Note that requirements for the host PC release differs on various L4T releases. You probably want the host PC to use Ubuntu 20.04.
