@Pedro Costa Welcome to Microsoft Q&A forum!
Please confirm, if you have a valid subscription and also is in active status?
You can create Azure Digital Twins service if you have a valid subscription. As per your statement above, it looks like you already have an account created with the same email id and free trial got expired.
If you upgraded from an Azure Free Account offer you will continue to have access to select free services for the remainder of the 12-month duration of that offer (beginning on the date you signed up for the Azure Free Account). Credits provided as part of the Azure Free Account will be automatically carried over but will expire 30 days from the date you signed up for the Azure Free Account. At the end of the 12-month period, your account will be billed at the standard Pay-As-You-Go rates. Microsoft reserves the right to change or discontinue any of the select free services or Azure Free Account offer at any time with or without notice.
For all the information related to Azure Free Subscription, please refer to Azure free account FAQ.
As an alternate, if you don't want to upgrade your free trial, you can create a new account and proceed with the documentation to Set up an Azure Digital Twins instance and authentication (portal)
Do let us know if you have any other queries.