If I cannot e-file a Petition to Accept Unintentionally Delayed Payment of Maintenance Fee in an Expired Patent (37 CFR 1.378(c), what other method of filing the petition is available?

You may file the same Petition via paper (users are advised not to use the e-Fillable Petition form if they decide to file by paper), however, the option of receiving an immediate automatic grant as one would receive in an e-filed petition is not available.

USPTO FAQ - Questions and Answers (2007JUN01)