High Sierra didn't convert my MacBook Pro 2017 to APFS

Hi guys,

I had MacOS installed on an external SSD (a HFS+ partition amongst other partitions on a Samsung T3 SSD) which was connected via USB 3.0 to my old MacMini, and I booted from there - ran perfectly. TimeMachine backups were done to a seperate, larger, partition on the same drive.

I then bought a MacBook Pro 2017 this year and installed MacOS from that time machine backup onto the SSD of my MacBook and got rid of the T3 SSD boot. Worked fine!

When I upgraded to High Sierra I was not able to upgrade to APFS. Neither the automatic installer did it, nor any update that came aftwards. When I boot into recovery mode and manually update to APFS, I can't boot from my mac. When i try to run BLESS manually I get an error message.

How to upgrade to APFS and be able to boot?