Install the latest update: 18363.628
It resolves the search box bug.
Just saw a solution in another forum and also this reason: https://www.heise.de/newsticker/meldung/Windows-10-Suchfunktion-derzeit-fuer-viele-Nutzer-kaputt-Workaround-verfuegbar-4653892.html (german - use browser translation features)
In powershell:
# startmenu empty fix
New-ItemProperty 'HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Search' -Name BingSearchEnabled -Value 0 -PropertyType DWORD -Force -verbose | out-null
New-ItemProperty 'HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Search' -Name CortanaConsent -Value 0 -PropertyType DWORD -Force -verbose | out-null
gps searchui | kill -force -Verbose
Has your Win10 Search box gone black? Does Search even work? | Computerworld
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