Not getting the CRM data to map the fields in Mail Merge Template

Hi Everyone,

I am facing the meta data issue with Mail Merge Template. Actually I am trying to create a Mail merge template I have downloaded the mail merge template from the CRM. When I opened it I don't get the Screen where we can map the fields and also ADD-Ins Tab in the same document. I tried with MAILINGS option there Address Block, Greeting Line and Insert Merge Field are disabled.

Could you please suggest me on this?

Thanks.