When I run the mod for the first time, it inserts this error into the log:
java.io.FileNotFoundException: C:\Users\adam5\Desktop\minecraft\modding\BetterAdvancements\Fabric\run\config\betteradvancements.json (The system cannot find the file specified)

But in this case, the mod does not automatically create the config file.

After testing some things, I was able to generate the config file by using the Mod Menu config screen and pressing Save and Quit

@MJRamon, thanks for providing the workaround. Indeed, this is a problem and it still exists for 1.20.2 for Fabric. I can confirm it. The game don't crash but it's REALLY annoying to see this entry in the logs.

@way2muchnoise, please, fix this little bug.

Fixed in 7d961a2