How to enable Search option for User Interface Text

Summary:

Hello,

I am trying to update wording for a Confirmation Pop-up which is configured via User Interface Text. However, when I enable the sandbox and go to Search and Replace option, "Search" button seems to be disabled/greyed out. I have tried multiple combinations for tick/untick options under Type as well as Match case/ match complete word or phase, but still Search button doesn't come up as enabled. This is the first time I am trying this feature, will appreciate if anyone can guide me what I may be missing here.

Confirmation pop-up message is configured when manager submits the job requisition.