ERROR can restart container (zpool was only 4GB why?)

lxc list
+------+-------+------+------+-----------------+-----------+
| NAME | STATE | IPV4 | IPV6 |      TYPE       | SNAPSHOTS |
+------+-------+------+------+-----------------+-----------+
| deb  | ERROR |      |      | VIRTUAL-MACHINE | 0         |
+------+-------+------+------+-----------------+-----------+
zpool list
NAME      SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
default  4.50G  4.36G   143M        -         -    40%    96%  1.00x    ONLINE  -

So I ran zpool set autoexpand=on default

lxc restart deb
Error: The instance cannot be cleanly shutdown as in Error status
Try lxc info --show-log deb for more info

root@host:/home/ubuntu# lxc info --show-log deb
Name: deb
Status: ERROR
Type: virtual-machine
Architecture: x86_64
PID: 143281
Created: 2022/09/04 18:11 UTC
Last Used: 2022/09/04 18:34 UTC

Resources:
  Processes: 0
  Disk usage:
    root: 3.15GiB

Log:

warning: tap: open vhost char device failed: Permission denied
warning: tap: open vhost char device failed: Permission denied

How do I view the error, restart it and why was the zpool only 4GB?

Try doing lxc stop -f <instance> that will do a forceful stop.