Hej all 
I am just trying out something with the v5.0.0-rc.4, and using a small template I have built for myself to get new projects started. In it, I have defined a very basic bluerpints/pages/default.yml
as follows
title: default-blueprint
image:
back: 'var(--theme-primary)'
color: 'var(--theme-accent)'
tabs:
content:
label: content
icon: text
columns:
main:
width: 2/3
sections:
fields:
type: fields
fields:
blocks: fields/blocks
sidebar:
width: 1/3
sections:
pages:
type: pages
template: default
This I then extend for blueprints like home.yml, as it will follow the same structure, but I want to change the name and icon of the blueprint—so, this is what I used to do before in v4, which always worked flawlessly:
name: home
icon: home
extends: pages/default
But now with the release candidate installed, opening a blank page with the home blueprint, the sections show the following errors:
Any ideas how that might come about?
Thanks already 
For completeness, here is the API request Kirby makes to try to load the sections
GET http://localhost:8000/api/home/sections/fields
which returns
{
"status": "error",
"message": "No route found for path: \"home\/sections\/fields\" and request method: \"GET\"",
"code": 404,
"key": null,
"details": []
}
After further investing, it seems not to be related to extending the blueprints, but just a general error, even when reducing the default template to
title: default-blueprint
image:
back: 'var(--theme-primary)'
color: 'var(--theme-accent)'
fields:
blocks:
type: blocks
the error No route found for path: "test/sections/main-fields" and request method: "GET"
presists
I cannot reproduce this. A blueprint with your provided code just works fine for me with Kirby 4 RC. Do you have any plugins installed?
I ran into the same issue with the kirby 5 official release. I had 3 plugins installed:
“tobimori/kirby-seo”: “^1.1”,
“bvdputte/kirby-fingerprint”: “^2.2”,
“tobimori/kirby-icon-field”: “^2.2”
deactivating tobimori/kirby-seo fixes the problem but I don’t know why. The plugin is listed as v5 compatible in https://plugins.getkirby.com/supports/5
You need the pre-release for Kirby 5, Releases · tobimori/kirby-seo · GitHub Or wait until the final release is published (probably very soon).
thanks, sonja
I was missing the pre-release version for kirby-seo (which still applies after v5 is officially out)