In the Magento CMS, a new feed must be generated before Tweakwise can read in a new feed with changes. If this is not done, Tweakwise keeps retrieving the old feed and the changes do not come through.
In Magento 1, you can adjust this in the module: System > configuration > Tweakwise > Export. There are two options there to start the export.
In Magento 2, you can adjust this in the module Stores > Settings > Confguration > Catalog > Tweakwise > Export. The ‘Schedule’ button ensures that a new export is started.