Unable to connect to SQL Server 2019 localdb

I'm part way through writing a .NET Core 3.1 Web API for a project. When I try to connect to the server, postman shows the following message:

Microsoft.Data.SqlClient.SqlException (0x80131904): Cannot open database "aspnet-53bc9b9d-9d6a-45d4-8429-2a2761773502" requested by the login. The login failed.

Login failed for user 'DESKTOP-RDBS4OR\Paul'.

I've looked around and the only things I can see are that I need to create a user for the db. I already have (the db uses the Windows Auth system) and the localdb has this user.

Looking at the throwback, I'm puzzled at the name of the DB - it's not the one in the connection string set in appsettings.json (below) or the referenced name win the StartUp class

"ConnectionStrings": {
    "quizzical": "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=quizzical;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"
},

Something is obviously not right, but I don't know what it is.

This is my first API I've done in .NET (I usually use php), so any tips on fixing this are appreciated.