Virto Cross-Site Lookup Selection column is provided by third party product. Q&A forum only supports Microsoft products.
You could go to virtosoftware for further help.
Please follow below steps to troubleshoot the OOTB lookup column issue.
1.Go to site collection features and deactivate the SharePoint Server Publishing Infrastructure feature.
2.Navigate to the URL http://site url/Relationships%20List/allitems.aspx and delete the list from the list settings.
3.Go to site collection features and activate the SharePoint Server Publishing Infrastructure feature.
4.The Relationships list will be created automatically. Then try to create lookup column in the list.
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