The gateway doesn't work !

Hi can you please help me with that error ?

i try to connect to Excel file , i copy the data source and all 

but i'm still cant refresh the that ,

look at the error that i get :

"error":{"code":"DM_GWPipeline_Gateway_InvalidConnectionCredentials","pbi.error":{"code":"DM_GWPipeline_Gateway_InvalidConnectionCredentials","parameters":{},"details":[{"code":"DM_ErrorDetailNameCode_UnderlyingErrorCode","detail":{"type":1,"value":"-2147467259"}},{"code":"DM_ErrorDetailNameCode_UnderlyingErrorMessage","detail":{"type":1,"value":"The credentials provided for the File source are invalid. (Source at u:\\maintenance\\shift_table\\timestamps_summary_update.xlsx.)"}},{"code":"DM_ErrorDetailNameCode_UnderlyingHResult","detail":{"type":1,"value":"-2147467259"}},{"code":"Microsoft.Data.Mashup.CredentialError.DataSourceKind","detail":{"type":1,"value":"File"}},{"code":"Microsoft.Data.Mashup.CredentialError.DataSourcePath","detail":{"type":1,"value":"U:\\Maintenance\\Shift_Table\\Timestamps_Summary_Update.xlsx"}},{"code":"Microsoft.Data.Mashup.CredentialError.Reason","detail":{"type":1,"value":"AccessUnauthorized"}},{"code":"Microsoft.Data.Mashup.MashupSecurityException.DataSources","detail":{"type":1,"value":"[{\"kind\":\"File\",\"path\":\"U:\\\\Maintenance\\\\Shift_Table\\\\Timestamps_Summary_Update.xlsx\"}]"}},{"code":"Microsoft.Data.Mashup.MashupSecurityException.Reason","detail":{"type":1,"value":"AccessUnauthorized"}}],"exceptionCulprit":1}}} Table: Not_Includes PM's.