I need a wordpress blog link to a website page fixed

General information for the website: The website displays a blog which is no longer linked to the wordpress blog site.
Description of every page/module: Blog page linked to a wordpress blog. The website is also wordpress.
Description of requirements/features: When posting on the wordpress blog it creates a blog entry but the url link it creates does not work any longer and goes to an error page. This previously worked up until Feb. Cant work out why its changed have tried changing the DNS settings (site is hosted by 1and1).
Extra services needed: 3rd party integration, Other
Extra notes: If you have time to fix this issue over the next day or two would be preferable. Please reply as to when you would be available to work on the job.