I've not been able to reproduce this on any of my development environments, nor on any of my production sites, so marking this as "Can not Reproduce" for now until some more troubleshooting can be performed on a site that it can be reproduced on (so it would be great if I can get an Admin Login for you site to do some quick troubleshooting, please start a conversation with login credentials and I can take a look right now).
I am also going to ask a few Premium license holders confirm whether its reproduce-able for them.
Example... I just created a new article as XenAddons Demos site and you can see that the "Leave a rating" button is visible.
And I was able to add a review (and since I have the permission to leave multiple ratings, the "Leave a rating" is still available.
My guess is that your issue has something to do with the new Lock/Unlock ratings feature (could be the new permissions have not been set or outdated templates so the new options on the input forums are not added).
First thing I'd look for are any outdated templates (or improperly merged templates) as there were additions made to the article add and edit forms.
Make sure that the new permissions are correctly set, that the Add article form hasn't been altered and that the "Ratings open" check box is on the forum and pre checked (if the input isn't on the form because of an outdated template, that Service that creates the article is going to LOCK ratings.
Can you confirm that you've set the new permissions for locking/unlocking ratings on an article?
Can you confirm that the add article input form has the Ratings open input on the form and is pre checked?
Can you confirm that the Article Tools dropdown has the "Lock ratings" or "Unlock ratings" links (those are controlled by the new permissions that you need to set).
Here you can see the "Leave a rating button" because ratings on the article are unlocked (the link in the tools dropdown says "Lock ratings" which means ratings are currently unlocked).
When ratings are locked, the "Leave a rating" button is not displayed and the Tools dropdown link says "Unlock ratings".
The Edit Article form also has the Ratings open option. Can you confirm that its showing up on your site?