Just in case any one else has this issue, the module is enabled but output is disabled. Prior to 2.2 you could disable output of modules via admin and while this menu was removed in 2.2 upgrade the previous settings were left unchanged.
If you connect to your database and run:
select * from core_config_data where path like "advanced/modules_disable_output/%" and value = 1;
you can see modules with disabled output.
Running:
UPDATE core_config_data
SET value = 0
WHERE path = "advanced/modules_disable_output/Magento_Review";
will re-enable the Magento_Review modules output. You will need to flush the config cache for the change to take affect.
Note that this will also affect the front end so recommend doing this in local/dev environment first so you can make any changes needed to css/templates to account for the new review elements on the site.
