Merge segment is greyed out

Question

I'm trying to merge four segments into one, but the option under File --> Project Settings --> Project is greyed out (just like "allow source editing"). 
 Any suggestions on how to enable this feature? 
 
 Thank you!

Paul · Answer

ANA ELISA IGEL 
 Was this a package you received from a client, or your own project? If your client didn't enable this then the option remain disabled for you. The reason for this is because not all filetypes should allow it unless you really know what you're doing and what the possible implications are. 
 Having said this some users may not even be aware of it and send out packages, disabling this feature, without even realising. So if it's a package you should probably speak with your client. 
 There's a little information here that might help understand this better: https://multifarious.filkin.com/2016/11/21/bridging-the-divide-merging-segments/

Paul · Answer

ANA ELISA IGEL 
 What happened to this question? 
 ANA ELISA IGEL said: the option under File --> Project Settings --> Project is greyed out 
 Is this no longer a problem? This setting has nothing to do with how many segments you are attempting to merge. 
 ANA ELISA IGEL said: What I just found out, though, is that you can't merge 3 segments at once, but 2. 
 This would be incorrect. For example, take this file: 
 
 I can do this: 
 
 I can even do this: 
 
 What version of Studio are you using? What filetype are you translating?

Trados Studio > 1. Trados Studio

Merge segment is greyed out