if your console's stuck on the bootlogo (switch2 ɴɪɴᴛᴇɴᴅᴏ SWITCH), one of these things are probably busted:
- your PRODINFO. (did you run a bricker?)
- your USER partition is unmountable. (If you resized it, are you sure you formatted it with the right BIS key?)
- your SYSTEM partition is unmountable. (Did you corrupt something?)
- your partition table is messed up.
- if you're using Atmosphere: you're booting it with a badly-formatted SD card, or corrupt Atmosphere files on the SD card. (via SciresM)
It means it is getting as far as loading BCT, package1/package2, and that's it. No titles load, not even fatal.
If you have an RCM-vulnerable Switch, you may be able to recover this; if your Switch can't boot Fusee from RCM, you're out of luck, unfortunately.
Try restoring from an eMMC backup. If you don't want to lose your data/progress, you can try restoring PRODINFO by itself, but that's a bit more of an advanced process.
If you don't have any backups ..... you have a brick. Your data can probably be recovered, but that is a bit tedious.
If your console is stuck on the Nintendo logo, you've likely corrupted one of the boot stages. You can restore the BCPKG2 partitions if you have a backup.