Hello @bean74695234 and welcome to MAAS community!
It feels that this error might be related to a network/firewall configuration.
MAAS generates grub.cfg that contains cloud-config-url parameter which is then used by cloud-init.
I’d suggest you to check what is being placed into the config and if machine is able to reach requested address.
You can do it either by adding some debug print statements here or in the grub boot menu or by listening TFTP traffic between machine and MAAS rack controller.
Also similar issue was discussed here