无法导入已有CCS项目，请问是什么原因？

在General类别下导入项目是显示
然后我按照提示在ccs类别下导入时提示
See details below.
Error: Import failed for project 'helloworld_evmc6678l' because its compiler definition is not available. The project does not appear to be a 'CCS Project'. Please try importing it through the 'General > Existing Projects into Workspace' wizard.