spotify embed code - follow widget is not working properly (follow-function)

[Alfonx]

Plan

Premium

Country

Germany

Device

Macbook Pro late 2013 and PC 

Operating System

Mac OS 10.14.6  and Windows 10

Google Chrome 87.0.4280.141

My Question or Issue

I used https://developer.spotify.com/documentation/widgets/generate/follow-button/ to create code to embed spotify artists on my website.

The problem is:
The "follow-function" of the widget is not working properly:

You can see a test here:

https://www.dj-nando.de/projects/testspotifyfollow.html

1. when I go to my page, it shows me the Spotify follow widget for five different artists. The widget only shows "follow" without a checkbox - you can't immediately see if you are following the artist or not.

2. now when i click on "follow" to an artist profile in the widget, i have to log in to spotify and after that "follow status" is correctly displayed to each artist profile on my page.
(this only works if i allow popups!).

3. an artist I already follow: if I now click on the widget "follow" on my website, the text changes to "unfollow". If I click this, the display remains afterwards however further on "follow", i.e. the function does not work correctly.

4. an artist, which I do NOT follow so far: If I click on the widget "follow" to this artist on my website, then a popup opens briefly, then it closes and it continues to say "follow" (without checkbox). I.e. the "follow" action did not work for this artist.

Checking the unfollow/follow-actions i did with the widget:

If I look directly into my Spotify account after performing point 3. and 4., I still follow the artist from 3. - i.e. the "unfollow" action did not work. Also the artist to point 4 was not followed, i.e. the "follow" action of the widget did not work here either.

[mazbehdjet]

Same issue. The code works on the Spotify Developers demonstration page but moving it to an external website the embed code does not work. Tried on multiple websites, tried the code given by the generator. Tried cut and paste of the code that works on the Spotify Developer page. Nothing works on external sites. Please can someone fix this?