In which state were you last based? Do you urgently need these funds in the next month? Did you ever buy any investment products through Marcus?
Given what you've said: file an online complaint with New York's Department of Financial Services [1] and the Office of the Comptroller of the Currency [2]. (You have no nexus with Utah. New York's DFS has teeth. I am assuming you lived in New York.)
Send a written letter (ideally with receipt confirmation) to Goldman Sachs [3]. Copy the DFS (yes, again), the FDIC [4], and Federal Reserve [5]. (No receipt confirmation needed for these.) Stick to the facts--the less emotion the better. Reference your last account statement, the withdrawal request (date and time, amount, confirmation number(s), et cetera), the dates and times you called and any other communications you made with Goldman, attempted or connected, and include a copy of your New York State ID. At the bottom of your letter, below the signature line, make note of everyone copied as you would in any formal letter.
Given Marcus's erratic behaviour and lack of communication unbecoming of a bank, there is a small chance there is cyber crime involved. Notify the FBI [6]. If you do, note it in your letter to Goldman.
[1] https://www.dfs.ny.gov/complaint
[2] https://www.helpwithmybank.gov/file-a-complaint/index-file-a...
[3] https://www.nmlsconsumeraccess.org/EntityDetails.aspx/COMPAN...
[4] https://www.fdic.gov/resources/consumers/consumer-assistance...
[5] https://www.federalreserveconsumerhelp.gov/about/after-i-sub...