Issue: Problem with VaultWiki

Hello! I have a problem with vaultwiki, it seems that every time I install it it doesn't let me access my index/forum page nor any pages and everytime I view my forum page I get a page with this message, Only admins can see this error. Other users can visit the site normally, but your immediate attention is needed in the AdminCP.

Invalid default namespace ID detected. Make sure that you have set up the default namespace via the Namespace Manager. If you have, it is possible that the Namespace Cache is not up to date because of a recent change or VaultWiki upgrade. To solve this issue, simply go to the Namespace Manager and select [Rebuild All Namespaces].

If you still receive this error after rebuilding namespaces, contact VaultWiki support. can you or somebody tell me how or if I can work around this and be able to access my other pages, plz? TY very much.^ ^