Error: object reference not set to an instance of an object error user mapping Quest Migrator for notes to SharePoint console' tool.

We are facing below issue while doing user mapping from Lotus notes to SharePoint 2016 OnPrem,

Error: "Object reference not set to an instance of an object" error while working on the user mapping using 'Quest Migrator for notes to SharePoint console' tool.

Before clicking on the migrate to SharePoint option we have done/configured the below setup a part of process,

 a) Set up wizard with necessary changes has been done,

 b) We have done Advanced configurations with SharePoint Site, given path of the user XML.

 c) We have selected all of the options under migration targets a) ACL entry mapping  and  b) SharePoint group mapping check boxes.

 d) Under Advanced security settings also we are not able to get the LN groups/Roles which are to be mapped to SharePoint groups.

 e) After all the above set up, once we click on the 'Migrate to SharePoint' we are getting the above error.

Thanks in advance.