You mentioned that you have an online account. If you check under documents, do you have your receipt notice there? This is what it states on our receipt notice.
We have extended the validity period on your Form I-551, Permanent Resident Card, (also known as a Green Card) for 48 months from the date of expiration. During this extension, you are authorized to work and travel. This notice, presented with your expired Permanent Resident Card, is evidence of your status and employment authorization. (This extension and authorization for employment and travel does not apply to you if your conditional permanent resident status has been terminated.)