SharePoint 2010: Error: Additions to this Web site have been blocked

Problem

A subcontractor has been provided administrator access to a SharePoint 2010 farm site and has been restoring content databases and configuring a new web application.  Performing routine maintenance and oversight checks, you attempt to make a configuration change to the main site collection and experience the following error:

Solution

1. Login to Central Administration under a farm administrator account.
2. Go: CA > Application Management > Site Collections > Configure quotas and locks.
3. From the Site Collection dropdown, select the appropriate site collection.
4. In the Site Lock Information section, set the Lock status for this site to: Not locked.
   
5. Click OK.

References

• Lock or unlock site collections (SharePoint Foundation 2010)
• Lock or Unlock site collections in SharePoint 2010