When you upload a relabel in file in the Manage Languages following the processes described in the KBA 2576546, the relabeling is not working.
Reproducing the Issue
You have performed the exact same steps described in the KBA 2576546.
1. Created a new custom language:
2. Downloaded the current language pack:
3. Found the label you want to change:
4. Put the new field label in a new file with the header of the file:
5. Imported the file for the new language:
6. Then, closed the browser and opened again, but the label hasn't been changed:
This is caused because there is an option to enable in the back end(Provisioning) to enable for the system to start considering the changes made by Manage Languages.
Go to Provisioning -> Company Settings and search for the option "Enable 3 tier Language Architecture Feature".
Now, go back to the instance and you are going to see that the system started to consider the relabeling made in the file imported:
3 Tier Language Pack, Manage Language , KBA , LOD-SF-PLT , Foundational Capabilities & Tools , LOD-SF-PLT-LAN , Issues with Translations (Language Issues) , How To