Can't use my PC port save with 3DS version

[FoxBlocks]

Whenever I try to use it, the game doesn't read it and overwrites it with a blank save. I know using a PC port save is possible, because I also tried using a complete save I downloaded on the Internet, and that one worked fine. So is there something wrong with my save file in particular?

Here's the save in case you want to take a look at it.
sm64_save_file.zip

[mkst]

Is it a save file from vanilla sm64-port? If so, it should work, as I have transferred saves between 3DS/PC and vice versa without issue.

If it's from e.g. sm64ex then that's why it doesn't work.

[FoxBlocks]

Yes, it's from the vanilla port.

[mkst]

And is this with 3dsx or cia?

[FoxBlocks]

3dsx