Content flagged as explicit is removed from the general streams, so your readers would have to sign up or log into an issuu account in order to have access to it. Your publication is not deleted from the issuu platform.
One workaround for you, would be to embed your publication on a website or blog, so your readers don't have to visit issuu at all in order to read them. The content warning will not show up on the embedded document, and your readers should be able to access it easily then.
Additionally, if you sign up for the Premium plan, you can easily embed your publications on your website and have more control over how your publication is displayed on your own website, without worrying about a content warning or users needing to sign in to view the publication. Embedded publications also tend to receive twice the number of reads as those that aren't embedded.
Please also see our Content Guidelines for information on what type of content can result in your publication getting flagged as Explicit/getting a Content Warning Message.