What should I do if the IRS can't find a 2023 amended return I mailed in from Germany? I tried the online service. The amended return results in an additional refund.

I sent the amended return in past the deadline for online filing in October 2024. The system asks for a Zip Code, which I don't have because I live in Germany. TurboTax informed me to submit the amended return because of a software error that didn't properly account for taxation in Germany of my SSI.