The interesting log is a bit later in the screen-n-cpu.txt:
Nov 02 09:13:25.177820 ubuntu-bionic-rax-ord-0021331595 nova-compute[23193]: 2020-11-02T09:13:24.491970Z qemu-system-x86_64: cannot set up guest memory 'pc.ram': Cannot allocate memory
So the hypervisor run out of memory.
The interesting log is a bit later in the screen-n-cpu.txt:
Nov 02 09:13:25.177820 ubuntu- bionic- rax-ord- 0021331595 nova-compute[ 23193]: 2020-11- 02T09:13: 24.491970Z qemu-system-x86_64: cannot set up guest memory 'pc.ram': Cannot allocate memory
So the hypervisor run out of memory.