SOLVED Two problems in one? (No Blocks Available / BTX halted)

[NasCon]

This pic is the result of a reboot (probably the first after upgrade, like I hear other say):

I can find info on both problems but not on the combination.
I have a HP MicroServer N54L. During boot I see all my drives (4 HDD's and an SSD) as DriveSmart OK.
My bootdrive is an USB stick that obviously starts booting since it seems to load ZFS...
Also the suggestion of using AHCI => that already was enabled in BIOS for ages.
What would be a logical path to follow?
Thanks!

 

[NasCon]

The BTX halted problem I have troubleshooted by re-installing freenas on a second USB stick.
I kinda hoped it would recognize the existing ZFS config, but no pools show up in the GUI.

I do have a backup, so recovering data is not the biggest problem, but is there a method to scan and rebuild the existing volume?
Or am I better off creating a new one? In that case, what is the recommended config? I have 4 1TB disks plus a 250GB SSD free in this system, and only 8GB RAM

 

[NasCon]

Refrained from any comments here, and after having searched endlessly and tried multiple how-to's and post also from this forum, I was not able to retrieve the config file from my USB stick. I took a plunge and at the risk of erasing my USB stick I did an update on the faulty stick. The config file was found and succesfully upgraded by a reformat and everything is working now.

Why is it SO hard to access a zfs volume? I could import it but nothing got browsable.
Learned a lesson in downloading the config file. Many thanks for all the help I got here...