Solved! Go to Solution.
You can re-link them by going into C:\inetpub\wwwroot\Builder\App_Data\Sites.xml and adding your sites tag back.
You can copy U3 site details and create another site tag. Please remember to change the Url and PhysicalPath attribute values to point to other websites
<Site>
<ID>20e948768a9840e18a0d08fb7f440595</ID>
<Name>U3</Name>
<Url>http://servername/Apps/U3</Url>
<PhysicalPath>C:\inetpub\wwwroot\Apps\U3</PhysicalPath>
<IsHostedOnIIS>true</IsHostedOnIIS>
<IISHost xsi:nil="true" />
<IISPort>80</IISPort>
<IISPath xsi:nil="true" />
<Description />
<ProductVersion>3.0.0.0</ProductVersion>
</Site>
<Site>
<ID>0f00b33b4f93477ca2abb895f56e34c2</ID>
<Name>s15</Name>
<Url>http://servername/Apps/s15</Url>
<PhysicalPath>C:\inetpub\wwwroot\Apps\s15</PhysicalPath>
<IsHostedOnIIS>true</IsHostedOnIIS>
<IISHost xsi:nil="true" />
<IISPort>80</IISPort>
<IISPath xsi:nil="true" />
<Description />
<ProductVersion>3.0.0.0</ProductVersion>
</Site>
You can re-link them by going into C:\inetpub\wwwroot\Builder\App_Data\Sites.xml and adding your sites tag back.
You can copy U3 site details and create another site tag. Please remember to change the Url and PhysicalPath attribute values to point to other websites
<Site>
<ID>20e948768a9840e18a0d08fb7f440595</ID>
<Name>U3</Name>
<Url>http://servername/Apps/U3</Url>
<PhysicalPath>C:\inetpub\wwwroot\Apps\U3</PhysicalPath>
<IsHostedOnIIS>true</IsHostedOnIIS>
<IISHost xsi:nil="true" />
<IISPort>80</IISPort>
<IISPath xsi:nil="true" />
<Description />
<ProductVersion>3.0.0.0</ProductVersion>
</Site>
<Site>
<ID>0f00b33b4f93477ca2abb895f56e34c2</ID>
<Name>s15</Name>
<Url>http://servername/Apps/s15</Url>
<PhysicalPath>C:\inetpub\wwwroot\Apps\s15</PhysicalPath>
<IsHostedOnIIS>true</IsHostedOnIIS>
<IISHost xsi:nil="true" />
<IISPort>80</IISPort>
<IISPath xsi:nil="true" />
<Description />
<ProductVersion>3.0.0.0</ProductVersion>
</Site>