.net - Can't compile a VS2013 WinForms project after adding a dll reference -

i have working vs2013 vb.net 3.5 project. when add , use 3rd party dll, project stops compiling. dll working in .net 4.0 windows forms project.

the error is

warning 95 namespace or type specified in imports 'stages.stagesgateway' doesn't contain public member or cannot found. make sure namespace or type defined , contains @ least 1 public member. make sure imported element name doesn't use aliases. c:\users\pvarma\documents\visual studio 2013\projects\safelink\safelink mas dev\stagesfunctions.vb 1 9 safelink mas dev

the compile fails @ imports stages.stagegateway statement.

how can fix error please?