Cancellation when payment failed

you can try another browser if you have trouble allowing pop ups and cookies, or use the phone or twitter (probably all explained above), but here it is again 

use a browser that allows popups and cookies and contact adobe support by clicking here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
in the chat field (lower right), type AGENT
be patient, it can take quite a while to reach a human

p.s you can also use phone (but chat is usually quicker), https://helpx.adobe.com/contact/phone.html

p.p.s. you can also use twitter to tweet @AdobeCare

p.p.p.s. if you're contacted by anyone (via email or private message), it's much more likely to be a scammer than an adobe representative. ie, double check for an employee badge if contacted in the forums and look for an adobe.com domain in the email address if you click reply to an email. then check again and be very suspicious. any other method of contacting (or offering to contact you) is almost certainly a scam, https://community.adobe.com/t5/using-the-community-discussions/staying-safe-in-the-adobe-support-community/td-p/12919684/redirect_from_archived_page/true

https://helpx.adobe.com/contact.html?rghtup=autoOpen

I found in another post here that this link is supposed to open a contact window, but it just redirects me to this customer help section where I can't talk to anyone

That depends on when you joined. 

You have 14 days from first download to cancel and request a refund.  After that, you pay a 50% early termination fee if you cancel before your 12th month of service.   To avoid penalty fees, wait until your 12th month to cancel.

===============
How do I Cancel my Subscription?
https://helpx.adobe.com/manage-account/using/cancel-subscription.html
===============
Subscription & Cancellation Terms:
https://www.adobe.com/legal/subscription-terms.html

CONTACT ADOBE SUPPORT:
================
Online Chat: https://helpx.adobe.com/contact.html?rghtup=autoOpen
Phone M-F, during normal business hours: https://helpx.adobe.com/contact/phone.html

Hope that helps.