SignalR was working while project was ASP.NET MVC3. Now i upgraded it to MVC5 (not so easy to do, I must tell you).
Then I noticed that signalR was not working. I we
You need to install Microsoft.Owin.Host.SystemWeb package in the project
Verify this link
If package is not installed then install the following package from the Package Manager Console (PMC):
Install-Package Microsoft.Owin.Host.SystemWeb
UPDATE
It purely says that, its not able to detect your startup class, here are few more findings.
This should definitely work, if it doesn't then try creating signalR in sample project.