PKHeX validates save files to prevent corrupt data from crashing the executable. Your save file lacks a proper checksum footer (last 0x200 bytes of a save file).
You can try transplanting the last 0x200 bytes from another save file (new, or someone else's) and it'll load in PKHeX, and probably will work on your console after exported from PKHeX.
(I overrode the footer validation, save loads:)