I downloaded Lightroom to a second device, and it’s requiring me to pay again. Help.

What @Rob_Cullen said.

Mobile subscription (via App Store) = Lightroom Mobile only

Desktop subscription (via Adobe) = Lightroom desktop + Lightroom Mobile

If you get a desktop subscription, you can cancel the mobile only plan.

A Google subscription will only be for mobile devices (phones, iPads).

You will need a subscription from Adobe for the "Lightroom Plan 1TB" (US$9.99/month. 1 Year Contract.) to enable use of Lightroom-Desktop on the Windows PC as well as all mobile devices.

https://www.adobe.com/au/products/photoshop-lightroom.html

Contact Adobe Support and ask if you can change your subscription.

You won't need two subscriptions in the long-run, but you may need to keep the mobile 'phone subscription' until your images are available in the Adobe subscription.

Contact adobe support by staying signed in to this forum and clicking here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
In the chat field (lower right of screen), Typing “Agent” into the chat text field will bypass the initial chatbot.
be patient, it can take quite a while to reach a human
If you are not able to get to the chat window, then disable your ad-blockers, firewall, enable cookies/scripts on your browser. If it still fails then change your browser/machine/network.