The m200 series player is really, really old and not really supported by SanDisk any more. Additionally, even when it was current there were 4 different hardware versions requiring 4 different firmware versions and quirky as all get out.
I believe the v2.2.5 firmware is the newest, so if you’re already running that, there is nothing to update to. Neither the SansaUpdater nor the special firmware updating software for the m200 series (sdmx3-iv001.exe) will re-install the same version or install an older one.
If your player is working OK, I suggest to leave well enough alone. If it’s not, be grateful it lasted so long, recycle it responsibly and update your player instead.