the %path% is a variable local to your personal computer - it isn't something dougeff can change.
*if* the path variable is the problem, i would:
1)uninstall all versions of the cc65 suite, including if one was bundled with that nestor thing. Just to make sure.
2)delete any leftover paths in the environmental variable (if any) leading to cc65 suite (you can use this guide:
https://www.computerhope.com/issues/ch000549.htm )
3)download and install the latest version of the cc65 suite.
4) is the problem solved?
5)if not: following the same guide, make sure the %path% variable points to the location of your new installation, and if it is not, make it so.
OR, just reference an absolute path to the (latest version of the) compiler and that should do it.