Hello @yara.garcia,
My name is Henry and I am happy to assist with your inquiry, and appreciate you contacting LastPass Support!
I am sorry about the issues you are having with your account. Please make sure to install the browser extension and logged in on it for the Autofill function to work properly. You can download the extension here.
Please let me know if this worked or if further assistance is required.
Thank you,
Henry | Customer Care