Jpdiag

The only writing at the bottom is the software version 2.0.5.3

Not that I noticed. I'll connect it again.

I tried with 2.0.5.3 today. Still can't reset the service light.
I did notice that the headlight test didn't work nor did the speedo test but when switching on the RPM it also turned on the headlight. 2.0.5.2 might have been the same, I can't be sure.

"i'd be curious to check on your computer what's wrong"

So would I. I tried again today with a Bluetooth ELM327 that I borrowed from my son and got exactly the same results. Can't reset service light but can test fuel pump, headlight, speedo and tacho. I'm hoping to borrow my son's laptop the next ...

Would it be worth trying M3C9? Although it seems too need a different licence file.

Tried again with .ddl files unblocked. No difference, still can't reset the desmo service.
I then completely uninstalled all of the Melcodiag stuff and did a clean install from the zip file into the Documents folder. Put the lic.le file in the same folder, made sure the .dll files were unblocked and ...

I think that may indeed be the problem. Both .dll files were "blocked". I have now unblocked them and will try again tomorrow.

How do I unlock the .dll files? Why would the installer install locked files?

I'm currently running 2.0.5.2, 2.0.1.5 was the test version you sent me. back in 2022. And yes I tick the M3C box.

No I don't have a newer OS. The Laptop I'm using won't support Windows 10 or 11. I'm a Mac user and don't want to spent a lot of cash on a Windows laptop that will get hardly any use.
I should add that my current setup worked perfectly well to reset the oil service light on my Supersport 939 about 3 ...