Problem is the incompatibility with Western, MENA and Asian version on the same computer as you have learned.
To work with an Asian version you have to install English version and Asian version, both!!!, and run with an English User Interface on your OS. Then InDesign takes the language of the OS.
thanks. How do I keep both versions installed? I've just installed the English version (without uninstalling the Japanese version) but now only the English version opens. Even when I switch back to Japanese in the CC Manager, I see InDesign installed but when I open in, the English version comes up.
UPDATE: Since I wasn't able to install the English version next to the Japanese one, I tried the folder hack again and this time it worked. So, for anyone interested:
1. Install the English version
2. Copy the content of the following two folders:
c:\Program Files\Adobe\Adobe InDesign CC 2015\Presets\InDesign Shortcut Sets\
c:\Program Files\Adobe\Adobe InDesign CC 2015\Presets\InDesign Workspaces\
3. Uninstall the English version
4. Install the Japanese version (or other CJK version)
5. Replace the "ja_JP" folders inside the two folders above with the "en_GB" (or "en_US") versions that you backed up from the previous installation.
Now your indesign should open in English with CJK tools enabled.
(Note: This worked for me only on a second try so I can't guarantee it will work for you.)
6. Extra step: If you're annoyed by having to do this every time you need to typeset in another script, please send a feature request to Adobe that we want an "all inclusive" version of inDesign that can work with all scripts! Feature Request/Bug Report Form
Install 1st language, switch in the CC app the language, now you can install the other language. Don't uninstall between, never copy parts of the programfolder from one place to the other.
The second instller will always install additional missing plugins into the first one. Do that.
I tried this but it didn't work... it just replaced the other version. Or if it didn't, it hid it somehow and I couldn't access it, it just kept opening the one that i installed later (even if I switched the CC language back). My solution may not be correct but it worked and saved my deadline I won't touch my install until I have to work with MENA again. Or until inDesign releases a proper combined version for all scripts - PLEASE, DO! :-)