I just double checked and the values are not being saved in the database.
Here's what I am doing to try and update the META keywords tag:
1) I created a special content section in Power CMS builder called meta-keywords for the home page
2) I log in to the admin system and click on the page optimization link to enter the part of the system where you edit keywords and I can see the original test keyword ("test") that I entered - I can also see this in the database table when accessing the mySQL database through Navicat.
3) I type in new keywords and click the save button - the page loads, everything disappears in the main window of the CMS admin system apart from a big green save button. I've tried clicking this button again - nothing happens, so I click on the home page link in CMS admin menu and click on Page optimization at the top again and see the same 'test' keyword I originally entered. I have also checked this in the database via navicat and can confirm the contents of the database have not updated.