Thanks for your reply, Leah Ju.
It wasn't a browser or cache issue that caused it. Work streams seem to be set up in a different way in Omnichannel admin center app than they are, in Omnichannel Administration app.
When I created the workstream in Omnichannel admin center app, the Channel field was set to Case, whereas when I look at the same record in Omnichannel Administration app, Channel = Entity Records and Entity field was blank.
As soon as I set the Entity field to Case, I was able to create a New Skill Attachment, but the assignment rule still did not work as expected. An agent who did not have the necessary skill still got the work item assigned in spite of the setting Matching Logic = Exact Match.
So, two things I am unsure about here,
1. Is this functionality missing from Omnichannel admin center app, or is there a different way to do it there?
2. If we do this set up in Omnichannel Administration app, it is not working because we are 'not supposed' to use this app or are we missing some other part of the set-up?
Thanks,
Shweta.