Update ticket tags through HTTP target extension (getting an error message)

Hi all,

I have been trying to add tags randomly to some tickets. I happily found this post: https://support.zendesk.com/hc/en-us/community/posts/360029308674-Using-Liquid-Markup-to-A-B-Test-Your-Triggers

I followed it step by step, but I keep getting an error message. I read all the comments in the other post but I couldn't find any helpful comment. 

This is what I get

HTTP/1.1 401 Unauthorized

PUT /api/v2/tickets/update_many.json?ids=13735 HTTP/1.1
Authorization: -------------------------
User-Agent: Zendesk Target
Content-Type: application/json; charset=utf-8
Content-Length: 0
Accept-Encoding: gzip;q=1.0,deflate;q=0.6,identity;q=0.3
Accept: */*
Connection: close
Host: saltpayco.zendesk.com

HTTP/1.1 401 Unauthorized
Date: Thu, 02 Sep 2021 18:25:35 GMT
Content-Type: application/json; charset=UTF-8
Content-Length: 37
Connection: close
WWW-Authenticate: Basic realm="Web Password"
Strict-Transport-Security: max-age=31536000;
Cache-Control: no-cache
X-Zendesk-Origin-Server: classic-app-server-655f74874f-6rjlv
X-Request-Id: 6888c8247efe60c1-DUB
X-Runtime: 0.046097
X-Zendesk-Zorg: yes
X-Request-ID: 6888c8247efe60c1-DUB
CF-Cache-Status: DYNAMIC
Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
Report-To: {"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v3?s=b88DcSOWw0SmCCX%2Fo7msapuIBGI%2FBBWnPTh3JH4L%2BKqopsdeauTEdMzRPG9P0RbncKisvrOly04P0M79LLDwcF3EAKbTup8P6sQM7qWIu%2FYfFxfjzwp78Ik4pilIjlFYRYhLIMcQQQ%3D%3D"}],"group":"cf-nel","max_age":604800}
NEL: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
Server: cloudflare
CF-RAY: 6888c8247efe60c1-DUB

{"error":"Couldn't authenticate you"}