[Moderator moved from Using the Community (forums) to Download & Install.]

Upgrade your OS.   El Capitan is not supported anymore.

Make sure your computer meets the minimum CPU & GPU requirements. Most Creative Cloud apps work on:
Windows 10 versions 21H1, 20H2, 2004, and 1909 (LTSB branches are not supported);
macOS 12 (Monterey), macOS 11 (Big Sur), macOS 10.16 or 10.15 (Catalina).
- https://helpx.adobe.com/creative-cloud/system-requirements.html
- https://helpx.adobe.com/indesign/system-requirements.html

If you can't upgrade to a supported OS and can't afford a new computer, cancel.  You have 14 days to request a refund.

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

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