Why do I get a message telling me that 'Required extensions are not installed...

Why do I get a message telling me that 'Required extensions are not installed' ? (OS9)

The earliest versions of the Sony plugins for ProTools on OS9 required a minimum set of extensions to be installed.
Please ensure you have the following extensions installed (run Extensions Manager from the Apple Menu to check):
CarbonLib
Open Transport
URL Access
QuickTime

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