We have an asp.net web application that works fine in our environment. One of our partners tries to the exact same code in their environment and can only process one request at a time. For example, there is only page that calls a long running stored procedure (5 minutes). If you call that page and the try to open a new page, the new page won't serve until after the first page has completed. We can see the request back up by looking at the worker processes for their application pool. They are running IIS 8.5 on a windows 2012 server. They're also running SQL Server 2016.
The database connection is structured the same as as in our environment. The stored procedure is not wrapped in a transaction. Any ideas what might be causing this behavior?