The DATEVALUE function returns an Excel date value (serial number) based on a date stored as text. However, it must be a valid text date which is determined by your date and time settings (national settings) on your operating system.
Microsoft recommends that you verify your date and time settings so they are compatible with the text date format. On a "Windows 10" operating system open the Control Panel and then "National Settings" and see if you can find a supported date setting. Both the short and long date must match.
I could not find a setting that worked with the text date above so I created the following formula in cell C3.