The most common trap those new to Blazor fall into is choosing the wrong template settings when creating a solution.
You have two [realistic] render mode options:
And one Interactivity Location: Global.
InteractiveAuto isn't a sane option. It's strictly for the experts [most of whom will avoid it like the plague because they know better]. It has very few use cases: a trap for the unwary. If you're reading this, you aren't one of those experts, so don't be tempted.
Why not Per Page/Component, surely it gives you more options? Many chose it, then code their first page with some interactivity, but fail to set the render mode on the page. The result is the page doesn't work as expected: buttons don't do anything.
The immediate solution is to set the render mode on the page. But that's almost certainly not what they really wanted. App and the layout are being statically rendered on every navigation event. Only the content pane is interactive [if you remember to set it]. This isn't a SPA, just fancy server side rendering with active areas on the page.
To resolve this, change the application to Global interactivity. Layout and App are interactive. You have a really SPA.
Add the render mode to the HeadOutlet and Routes components in App.razor.
<Routes @rendermode="InteractiveServer" /> // Or <Routes @rendermode="InteractiveWebAssembly" />