If users in a suborg are not getting the Read&Write for Google Chrome extension with unlimited licensing, this is typically due to inherited permissions are not being applied. The OU that the users are in is likely not inheriting permission from higher level OUs.
You can check this by going to the Google Admin Console and follow these steps:
1) Go to Devices > Chrome Management > User & browser settings
2) In User settings, locate the OU or suborg and click the name of the unit
3) Under each heading you should see Inherited
If it shows as Locally applied then the org is not inheriting permissions from the OUs above. Please read Google Support article Tailor service settings for different users that shows how to change the permissions.