When generating a Quartus II MegaCore IP design, it fails with the error "the device family **** could not be read". Why am I getting this error?

In some cases, if the device information is not installed, MegaCore will display an error "the device family **** could not be read" and will not be generated.
(Depends on MegaCore type)

In Quartus II Ver.10.1 or later, it is divided into multiple files to reduce the file size when downloading.
After installing Quartus II, you need to install the device information separately. Also, when installing, the device information is selectable, and it is possible that the corresponding device information has not been installed.

First, please check if the device information for the corresponding device is installed.