Problems with Alexa Blueprint, error message

Hi,

at this time I need your help to get it work with Alexa. The audio generation works like a charm. At my next step i like to make a blueprint for ALEXA.

Here is my Problem:
if I login on: https://blueprints.amazon.com , I follow your guide to create a blueprint, but at the point were I have to fill in the Feed-URL this error appears:

————
Feed is malformed and cannot be parsed. Please make sure that the feed is a valid RSS format.
————

I have read a lot in the developer docs, but don’t find an answer, found two forum postings were they discussed about the formatted date in the feed which maybe the problem, however it don’t work.

What I have try till now:
– change the date in needed format like in your docs -> not work
– check feed with validators, 100% valid

because the site is in coming soon modus, here the content
https://pastebin.com/pzaudzeH

Further question:
is it a problem when my Alexa Account is on Germany ? – Because when I switch to blueprints(DE) the blog feature is not available

is the language tag in feed the issue ?

is there a possibility to get further information about the error in view of the malformatting ? to find the error ?

thanks for helping …