Unfortunately, I don’t have enough information to tell you what is causing the problem.
Can I access this page somewhere to check it out? What is the URL?
It is interesting because the screenshot shows “Search Result” (without s), but the plugin creates a results page with the title “Search Results” (plural).
You may try deleting the page with the permalink “search_gcse” from your WordPress pages and deleting it from the Trash as well.
Then deactivate the plugin and activate it again.
The plugin will then re-create a page with a permalink of “search_gcse”. Maybe something went wrong on this page and re-creation will solve the problem.