The Frenchman had qualified 18th for Sunday's race in Baku and is now set to start last.
The governing FIA's technical delegate reported in a note that a deflection test of Ocon's rear wing had exceeded the permitted limit.
Stewards said Haas had explained the discrepancy as due to a problem with the assembly of the specific part.
Haas are ninth in the 10-team standings and 11 points behind closest rivals Sauber.