There was no error showing on my Crossplane CompositeResource but one of the resources was not being created. No errors in the Crossplane log: kubectl -n crossplane-system logs -lapp=crossplane --since=1h

A helpful person on https://crossplane.slack.com/ssb/redirect pointed out that I needed to run crossplane with args --debug in order to see the error message. This surprised me, I am used to --debug being for relatively obscure information but now I know that in Crossplane this is not the case. Details here: https://github.com/crossplane/crossplane/discussions/4886