Web API in MVC Project isn't hitting breakpoints ("symbols not loaded")

Until you find a permanent solution you can use the method System.Diagnostics.Debugger.Break() to force a break to occur on that line - just like a breakpoint:

public ActionResult IndexCheckInOut(string providerKey, DateTime? date = null)
{
    System.Diagnostics.Debugger.Break();   
    return View("Index");
}

Here are some links to articles that might help you find a more permanent solution:

The breakpoint will not currently be hit

Stepping into ASP.NET MVC source code with Visual Studio debugger

Possible solution: I had forgotten that I was previously doing some remote debugging and had set debug symbols to be loaded from a UNC path instead of the Microsoft Symbol Servers.

To fix this head to: Tools -> Options -> Debugging -> Symbols -> Make sure 'Microsoft Symbol Servers' is checked.

I also found this issue from creating a new Solution Configuration and not basing it on any existing configuration, such as the DEBUG configuration. That caused Debug Info to be set to none.

To fix this: Right-click your project -> Properties -> Build -> Make sure your faulty Solution Configuration is set -> click Advanced -> change Debug Info to full.

For me it worked out to just stop IIS and restart Visual Studio. Definitely worth a try before further investigation.