sublimetext3 - Sublimerge won't work on scss file -

i installed sublime text 3 , sublimerge reason cannot compare .scss file. not sure did wrong because default. if copy , paste both files untitle tab compare, works.

is there settings supposed change?

update

here steps:

1. download sublime text 3 mac

2. install package control

3. install sublimerge pro

4. open .scss file github reop locally

5. download folk of repo in .zip , expand different folder

6. open same .scss file in folked repo

7. compare view

8. the new window opens there no diff although different