Write to the Vatican
Should a member, or a group, of the Faithful in the Diocese desire to continue their appeal after the Bishop has refused to grant it or refused to respond in the allowed period of time, they may write directly to the Holy See in Rome, to the appropriate Dicastery. The assistance of the local pastor, if this issue affects a parish rather than an individual, may be needed.
Steps to take:
Write to the Prefect of the appropriate Dicastery (likely, this will be the Dicastery for Divine Worship and the Discipline of the Sacraments, or the Dicastery for Bishops).
Be clear and to the point about your concern and about what you desire for the Dicastery to do.
Include any documents that will help the Dicastery understand the situation and what has transpired in its regard.
Include the available means for the Dicastery to reply to you, which will typically be by mail.
Expect several weeks for the Dicastery to receive your letter. If it is a pertinent case, expect several weeks for the reply to arrive in the mail.
Address:
His Eminence, Arthur Cardinal Roche, Prefect
Dicastery for Divine Worship and the Discipline of the Sacraments
00120 Vatican City
(Italian: Dicastero per il Culto Divino e la Disciplina dei Sacramenti; 00120 Città del Vaticano)
Address:
Prefect
Dicastery for Bishops
00120 Vatican City
(Italian: Dicastero per il Culto Divino e la Disciplina dei Sacramenti; 00120 Città del Vaticano)
Best Approach:
Send the letter through the Apostolic Nuncio in Washington, DC
Send a package to the Nuncio that also contains the package for the Prefect within it
Include, for the Nuncio, a copy of all documents contained in the package for the Prefect
Include, for the Nuncio, an explanation of your request to the Prefect
Ask the Nuncio to send the internal package to the Prefect in Rome
The internal package should already be addressed to the Prefect and contain, in a sealed and addressed envelope, all of the documents ready for the Prefect.
Typically, documents are sent between Rome and the Nunciature through diplomatic packages on a frequent basis.
Use a formal letter form, where you include the date and your return address on the letter as well as the formal name and address of the recipient.
More information:
https://www.cultodivino.va/en/chi-siamo/organigramma/superiori/prefetto.html