Abstracts/submissions which are assigned won't be unassigned from someone automatically even if they have updated their topics/expertise. The reasons include that they may have already submitted reviews on some of those abstracts/submission, they may have wrongly changed the topic among other possible reasons we never made the unassignment automatic.
For unassigning abstracts/submission manually, you can do either of the following:
Method 1:
Go to Manage/Assign submission
Select abstracts/submission which you want to unassign (you can select up to 30 abstracts/submissions at once)
Click on "Assign Reviewers" button in the top right corner
Select the reviewer's you want to unassign from the selected abstracts/submission
Click Unassign
Method 2:
Go to Contacts
