I use VisualBoyAdvance-M v2.1.9 emulator (with an "M" at the end of VisualBoyAdvance) on my Windows 10 computer and the save file loads and saves properly.
yea well what operating system are you using since you did not mention that in the first place, which is also equally unhelpful
also try running VisualBoyAdvance-M from another computer or a different OS platform such as Windows or MacOS
I run the VBA-M app from a folder or path with a "short" name that doesn't contain spaces in between (never using folders with really long names or paths), on SEVERAL Windows based computers and they all work correctly, including game saving & loading.