.  ssc install mypkg
checking mypkg consistency and verifying not already installed...
all files already exist and are up to date.

. mypkg
command mypkg is unrecognized
r(199);

如上所示，下载mypkg,显示命令已存在，但输入命令却报错199。将文件夹里的mypkg删掉后，重新下载，还是会报错199，请问这是什么问题