Are there any circumstances when a public or a private entity is not required to provide effective communication?

Yes, public and private entities do not have to provide an auxiliary aid or service if doing so would create “a fundamental alteration” in the goods or services being offered or would result in an “undue burden” which means “significant difficulty or expense.” However, they still must do their best to provide a different auxiliary aid that would ensure effective communication if at all possible. And state and local government agencies have to do a bit more explaining why not than private businesses do.