I got the same question. It seems happened for a while. When can this be fixed ? We are not be able to use old UI forever. Or is there a work around instead. If yes, please provide detail steps.
Here are people met same issues,
I saw a lot of persons met same issue, and someone says that download toolchains can fix this problem. Can anyone provide detail steps of how to install this toolchain? I also download that, but don't how to install this toolchain with arduion IDE ??