If contribution to the profit sharing, per the plan document, was voluntary, then there is probably no disqualification event that could be corrected through EPCRS. If the Plan is worded in a way that the employer is mandated to make a certain level of contribution, then EPCRS might be available to make it retroactive. You haven't put enough facts out there to make a clear determination.
Note that I doubt that you could amend prior tax returns to take the 404 deduction in a prior year.
I am sorry to hedge, but you will need to get legal counsel involved with this kind of EPCRS correction.