N64 core not working

I'm having trouble getting the Mupenplus core to work for my games. I have NES, SNES & Genesis games working but anything N64 is not. It was working yesterday but suddenly stopped working. I've searched through log files to try and figure out what is happening and this is all I could find.

This comes from retroarch.log when I try and load the core directly from within Retroarch.

[ERROR] Failed to open libretro core: "/tmp/cores/mupen64plus_libretro.so"

[ERROR] Error(s): libpng12.so.0: cannot open shared object file: No such file or directory

I've looked in that location and it is there. I've tried using Retroarch's online updater to update that core. It still gives that message.

Can anyone suggest a solution? I'm running an Intel i7 PC with LibreELEC 8.0.2 (I think)

I've also pasted my logs to HHVH

Thank you.

Great. I will try that a little later. I did use the online updater. Didn't know otherwise.

Thanks for the help.

Thank you!

Deleted the relevant files and rebooted and it works!

So simple now that I know.