The "merge" option is greyed out

Hello,

I would like to merge two entries in my Termbase. I found these instructions, but at Step 3, "merge" is greyed out in my menu. I feel I must be missing something obvious, but I have tried several things and am not getting anywhere.

I am using Multiterm 2017.

Example of what I want to merge:

Term 1

  • French: responsable direct
  • English: Direct Manager

Term 2:

  • French: responsable hiérarchique
  • English: Direct Manager

 

I have opened both entries, but the "Merge" option in the menu is greyed out:

 

Can anyone point me in the right direction?

Thanks!