An error has occurred in the search system
Resolution will depend on the actual underlying error.
For a more detailed error message:
Examine the HTML page source - more detailed information may be output in the HTML source.
Examine the JSON or XML output for the query and examine the padre return and address the error as appropriate.
modernui.Public.loglocated with the collection logs section of the log viewer (from the administration interface) and address the error as appropriate.
Try accessing the page and viewing the HTTP response code (e.g. access the page directly from your browser and inspect the headers).