An unhandled exception occurred while processing the request. – Blazor

An unhandled exception occurred while processing the request.
NullReferenceException: Object reference not set to an instance of an object.
Microsoft.AspNetCore.Components.Routing.Router.Refresh(bool isNavigationIntercepted)

Erro causado provavelmente por ter rotas com caminhos iguais.
Verifique suas rotas adicionadas recentemente.

No meu caso estava ocorrendo erro 500 no console.

Error caused probably by having routes with equal paths.
Check your recently added routes.

In my case, error 500 was occurring on the console.