Why am I unable to merge records in Vtiger CRM?

If you are unable to merge records in Vtiger CRM, it maybe  you don’t have the Merge privilege enabled for your profile. 
To give a user access to the Merge option in Vtiger CRM, follow these steps:

1. Log in to your CRM account.
2. Click the User Menu 
3. Select Settings. The Settings page opens.
4. Go to User Management > Profiles. The Profiles page opens.
5. Click Edit next to the profile for which you want to enable merge access.
6. Select the respective App.
7. Choose the relevant Module, then go to Field and Tool Privileges.
8. Search for Merge.
9. Enable the Merge checkbox.
10. Click Save.

Once saved, users with that profile will have access to the Merge feature in the selected module.