I have set up rules using List Forms Extensions (such as hiding a field or disabling it) but they are not actually being enforced. Why are they not working?
List Forms Extensions does not support SharePoint list forms that have been customized using Infopath. The rules will currently only work using out of the box forms. Infopath also does provide the capability to hide and disable fields so it would have to be one or the other in this case, you would have to choose between using an InfoPath form or List Forms Extensions.