I used Ubuntu to format the HDD into ext4. With Terminal I changed the privileges and gave read and write access to the parent folder and the child objects within. After that I could copy files to the HDD.
But after connecting it to my Formuler1 the HDD still would not mount. Under OpenPLI 4 the hdd would mount. It is only after updating to OpenPLI 7.1 I can't mount it.
Strange.
I used another HDD, 3TB and formatted it exFAT and named it 'movies'. Connected it to the Formuler1 and it mounted. So I guess it has to be the way the 4TB HDD was formatted.
So I logged in with my Mac to Formuler1 as a server, and could choose between the options 'root', 'EFI' and 'movies'. I had formatted it 'movies' with 1 partition but when logged in as a server there also was a partition named 'EFI'. When I logged in with my Mac to Formuler1 with the 4TB HDD connected I only could choose between the options 'root' and 'movies'. No 'EFI'.
When I formatted the 4TB HDD again I could still not mount it but when logged in as a server there was no EFI.
What is wrong with the 4TB HDD that makes I can't mount it?