@user17553787901 , first we need a few bits of info ( to be able to focus the answer to your situation).
(a) When fid you enter this country with F-1 ---- trying to understand whether you are still in or out of exemption period ?
(b) Which country are you from --- need to see the exact wording of the tax treaty ? Many treaties allow for an exclusion from US Tax of a fixed amount. Thus form 8233 may not be applicable
(c) If you are still in the exempt, you will have to file form 8843. And of course if you are NRA at any point during the year ( depending on exact facts and circumstances ), you may have to file 1040-NR ( Not supported by TurboTax --- use SprinTax or similar ) or dual status ( 1040 + 1040-NR).
(d) During OPT, you are exempt from FICA
(e) Note even during OPT you are not an employee but a trainee -- there are differences for tax purposes ( FICA/ vacation/overtime-pay etc.etc. )
(f) Do not understand whereon form W-4 you entered NRA -- 4c is for extra withholding.
I will circle back once I hear from you --yes ?
