Found a solution here: Cortana not finding Desktop apps when searching for them
Here is the relevant part:
I reinstalled [Cortana] using the following procedure:
- Open an elevated CMD window (press win + X, and then press A)
- Type 'start powershell' (without quotes) and press enter
- Run the command:
Get-AppXPackage -Name Microsoft.Windows.Cortana | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
After 30 seconds the problem was solved on my machine. Finally!