Personally, Minix 3.2.1 does not work for me on Virtual Box 7 on a Debian Linux 12 amd64 host. I get a fatal error trying to start the Minix vm after Minix is installed.
However, Minix 3.1.0, 3.1.6, 3.3.0, and 3.4rc6 work for me on Virtual Box. And I have Minix 3.4rc6 running on my laptop bare metal; however, lately it is built from minix 3 git master plus some of my own changes.
I would verify that internet is working. Use ifconfig to see if you have a valid ip address and use nslookup
pkgin.net
I tried to figure out how to change a path to a different repository in pkgin but I could not.