Recently I did an erase of the internal HDD on the iMac - planning to clean install upgrading from Mojave to Catalina. (I have done a clean install with every upgrade, so the process is not new to me.)

I did the erase . . . then trouble. The HDD cannot be found when trying to install the new OS. Only the SSD (fusion drive) shows up as an option. The HDD appears in Disk Utility, but as "uninitialized." Any effort to erase and reformat leads to error messages. Partition option is greyed out.

I went to Terminal. Tried to erase and reformat from there, but get the error message: "Cannot write to the end of blocks."

So . . . Is there any way I can FORCE the HDD to be detected and reformatted . . . ready for the Catalina install? Some other 3rd party tool? Note: I tried DoYourData Super Eraser, but it does not recognize the HDD on the computer, only the SSD (fusion).

Any solutions out there?


Many thanks,
MG2009