A family of Microsoft on-premises document management and storage systems.
Please check as following:
1.Make sure we send document from one library to another at the same web application.
2.Enter the correct library url when using <send to>
For example:if you want to send the file to the library ‘test’,you could enter the URL as it shows:

If you just want to copy files to other libraries, you could also try the following method:
1.Select content and structure in site settings, choose the document you want to copy:

2.Click copy in the action ribbon:

3.Select the target library you want to copy to:

Note: If you don’t see content and structure, please activate Site collection features> Office SharePoint Server Publishing Infrastructure and Site Feature (on the specific site) - Office SharePoint Server Publishing.
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