5.10 General provisions governing periods
5.10.004If you miss a time limit, legal sanctions are applied, such as refusal of the application, deemed withdrawal of the application or a (partial) loss of rights, for example a loss of the right of priority due to late filing of the priority document.
GL E‑VIII, 1.8
If you consider that the EPO's finding is inaccurate, you may, within two months after receiving the communication noting the loss of rights, file a request for a decision on the matter. A decision will be taken only if the EPO stands by its opinion. Any such decision is open to appeal. If the request is allowed, no decision will be taken and the EPO will inform you that the loss of rights has been set aside.