Gene Heskett composed on 2019-04-02 21:50 (UTC-0400):
I have never had ant great success at pre-partitioning a drive, the installer never accepts what you so carefully lay out
This should not be. I *always* partition in advance, never have a problem with any Debian installer using partitions as I specify. Maybe you should try again, but before trying installation, after partitioning, show us output from:
parted -l and/or fdisk -l
to see if that's where your trouble lies.