I open the app and it says that might pay for a subscription.

if this isn't a lightroom mobile issue:

start here - https://helpx.adobe.com/manage-account/kb/stop-creative-cloud-trial-mode-after-purchase.html

IF your account shows an active subscription and the above fails to help:

proceed to these steps - https://helpx.adobe.com/enterprise/kb/resolve-trial-and-license-expired-errors.html

if that fails, https://helpx.adobe.com/download-install/kb/adobe-license-issues-keychain-credential-mgr.html

below are solutions some users reported:

if those all fail, change your cc language. eg, try international english - https://helpx.adobe.com/creative-cloud/kb/creative-cloud-trial-mode.html

if that fails, change the install location

Hello @misael_1015 

Please see this page for info and try Restore Purchase.  Please make a note of any error message

https://helpx.adobe.com/lightroom-cc/kb/lightroom-mobile-in-app-purchase-issue.html 

If this does not help, please contact Adobe Support directly, as this is a user-to-user help forum.  Contact Adobe Support at https://helpx.adobe.com/contact.html?rghtup=autoOpen