Unable to change Incident status from Assign to any other statues

Hi Team.. I am using demo version. I changed incident status from New to Assign, and then I am not able to change to any other status, there is no operation drop down available to select any other status.  I am an admin and I checked incident workflow as well, which is setup as default. As per workflow, I should be getting option from Status Assign to be changed to Duplicate, Ready for Retest and Not Reproducible.

Thanks in advance for any help and support.