What should we do when an abstract gets accepted for a conference, but the material is not ready?
I suppose that standards differ, but in my experience (CS) posters don't need to be all that refined. Unless your standards are different, I suspect that you could put enough together to inform people about your project, its current state, and its direction, if not the conclusions that aren't yet ready.
Many posters are &quot;work in progress&quot;, rather than completed.
Alternatively you can withdraw if it is impossible to do enough to meet your own standards.