Applications Cannot Connect After Migrating Databases with Powershell dbatools

I'm attempting to decommission an old SQL 2008r2 server by migrating databases to an existing SQL 2012 server in my environment. I used dbatools in powershell (Start-DbaMigration -Source OLD-SQL -Destination NEW-SQL -DetachAttach -SetSourceReadonly -Force). The process completes and the properties of the databases on the new server appear to be the same as on the old server but my applications cannot connect to it.

I tried setting up a SQL alias using cliconfg.exe (both 32bit & 64bit) on the servers running those applications (Sharepoint 2010 and a homebrew application created years ago) but they still cannot connect. With the alias in place I'm able to view the databases on the new SQL server by opening a .udl file to the old server's name and the connection tests fine.

I don't care too much about Sharepoint but the developer for the...