When regenerating , please use the STM32_USB_Host_Library presented on https://github.com/STMicroelectronics/stm32_mw_usb_host/tree/master.

1. On the folder stm32_mw_usb_host/Class/ leave only the MSC folder.
2. On the IDE delete all dependencies of the deleted classes on step 1 in case there are some errors about file not found
3. On the file usbh_msc.c , go to the function uint8_t USBH_MSC_IsReady(USBH_HandleTypeDef *phost) and change MSC_Handle->state == MSC_IDLE into MSC_Handle->state == MSC_USER_NOTIFY.

Notes:

-Files explorer.c/.h , stm32746g_discovery_audio.c/.h and stm32746g_discovery.c/.h were taken from the example Audio_playback_and_record , thus they are not generated by CubeMX. -On this example CubeMX 6.9 was used. After code generation a lot of work was still needed to get the app to work. I hope this is fixed on newer versions.