This may be due to the fact that the parameters apply to 17.0.1 issue of Mabox.
It may be version 17.0.3 now. Can you check the other (main) link on the new parameters to boot up if you are using the newer version? And note you will need to use the right grub in the correct mode (uefi or bios-legacy).
In GPT partitioning and UEFI, you will need to select a FAT32 partition ($esp) as mount point for /boot/efi (and boot up in uefi). If you want to use GPT and bios-legacy (I don’t recommend it for you); you will need to have a bios_grub partition and flagged as such to install (and boot up in bios-legacy).
There’s your mistake here.
Oh, best to prepare all partitions before OS installation.
And another thing, I (and most) people don’t use LUKS encryption. I (and most people) cannot help you with it (but I don’t think that is your current problem).