Occasionally a creation is blocked or rejected. There are a few possible reasons.
Some models on NightCafe are run by external providers (the companies that make the models). Those providers apply their own content filters and may block a prompt or the resulting image on their side. NightCafe has no control over this — so if one model blocks your prompt, a different model may still work.
All creations must follow NightCafe’s Community Standards. Content that breaks them can be removed by moderators.
Some community/custom models can produce NSFW results even from innocent-looking prompts, because they were trained on more NSFW data. Turning on the NSFW safety option adds negative prompts behind the scenes to help prevent accidental NSFW creations.