Boggler_Crunchy

Tried opening this in PKX Delta (should've honestly thought of that earlier) and yeah seems to confirm that this file is probably done for.

Can't say I have a solution for you, but I did just wanna chime in to say I'm having a very similar issue with a copy of Ruby and a FireRed Romhack. Game acts like there's no save file when loading, and PKHeX also throws an error when trying to load. I haven't heard back from anyone, probably since mine was an instance of SD card corruption, but I hope you're able to salvage your save.

I started playing on a GBA Flash Cart recently. It works great but the crappy sd card reader it shipped with corrupted my sd card. I was able to recover the saves from it using some free software (forget what it was unfortunately) but all save for one are completely unreadable by either the Flashcart, Mgba, or PKHeX. The save file I'm trying to recover, which is a vanilla+ style rom hack of FireRed found on Pokecommunity here, is compatible with PKHeX as far as being able to read the save but no luck, I get the error saying that the save file is corrupted. Looking at it in a hex editor looks like the data wasn't completely wiped which gives me some hope, but I'm not quite as knowledgeable about save file structure in the Gen III Pokemon games and googling has left me with more questions than answers. I'd greatly appreciate if someone could at least take a peak to see if it's salvageable. I think recovering the whole save is probably a fools errand but I'd at least like to get the Pokemon in my PC off of it if I can. Pokemon FireRed LeafGreen Plus.sav