Trial version issues

Looks like someone, perhaps you, had a trial before on this computer. Trials are NOT for doing projects or schoolwork. They exist only to try-before-buying. $30 per month will get you InFesign and the ability to cancel any time (the $20 program is a promise to pay for the year) 

Only one trial is allowed per computer. If you had a trial previously, you don't get a 2nd one.  Sorry. 

Qualifying students & teachers save 60% off regular Creative Cloud rates for the first year of service.   Certain restrictions apply. See links below.

https://www.adobe.com/creativecloud/plans.html 

https://www.adobe.com/creativecloud/plans.html#ccm-ste-introductory

This is a public forum, not Adobe support. Users here can't provide support for account, subscription, or billing issues.  Click the following to contact Adobe customer support staff for help: 

https://helpx.adobe.com/contact/support.html

You must be signed in with your Adobe ID and allow cookies in your web browser for this to work. Click the chat icon at the bottom right of the page to open a chat session. Typing AGENT into the chat window should connect you directly to a CSR rather than the AI.

I am not familiar with InDesign, but I suspect like most Adobe products it is not possible to open a file created using a later version of a product with the earlier version. That is to say, you can use InDesign 2020 to open an InDesign 2019 file, but it is unlikely you will be able to use Indesign 2019 to open an InDesign 2020 file.