Multisite homepage directing to domain_current_site

I am trying to configure the Domain Mapping plugin for a multisite installation. I have followed the instructions, but my blog homepage is directing to domain_current_site, as opposed to the correct URL. I have confirmed that I am setting this properly in wp-config. Any ideas how I might resolve this issue? Thanks in advance for your help – it's a great plugin (I've used it successfully on other sites in the past).