Url.Page suddenly started to omit top-level domain

Question

I have a site up and running and I believe I changed nothing about this code, but suddenly Url.Page and other methods started to create URLs without the top-level domain.

For example:

callbackUrl = url.Page(
    "/Account/ConfirmEmail",
    pageHandler: null,
    values: new { area = "Identity", userId = user.Id, code = code },
    protocol: "https");

1-2 weeks ago: https://example.com/...

now: https://example/...

I have absolutely no idea why this happens all of a sudden. I'm looking for ideas! Thanks!

PS: No clue if this helps, but my setup is: ASP.NET (C#) razor pages -> kestrel -> nginx -> cloudflare

Answer 1

I reconfiguered my Let's Encrypt SSL certificate with certbot on the website, which happened to change the reverse proxy entry in my web server configuration. The reserve proxy then showed to "http://example" instead of "http://localhost:5000" like it's eg required for the Kestrel/Nginx combo. So I just had to revert this change and it worked again.