latest_receipt_info comes as null in Testflight

I am verifying the receipt server side and today I noticed that the latest_receipt_info field in the verify response is null, which means I can't verify the receipt and process the transaction. This happened in the TestFlight environment, I am afraid that it could happen on PROD. Do you know why this might have happened and how do you verify your receipts?

I am using Java and this is my code for verification:

IosVerifyReceiptResponseDTO response = restTemplate
        .postForObject(iosLiveVerifyUrl, request, IosVerifyReceiptResponseDTO.class);

if (response != null) {
    if ("21007".equals(response.getStatus())) {
        log.info("Sandbox is on");
        response = restTemplate
                .postForObject(iosSandboxVerifyUrl, request, IosVerifyReceiptResponseDTO.class);
    }
}

if (response != null && response.getLatest_receipt_info() != null) {
    log.info("Processing subscription");
    LatestReceiptInfoDTO latestReceiptInfoDTO = response.getLatest_receipt_info().get(0);
    long expireDateMs = Long.parseLong(latestReceiptInfoDTO.getExpires_date_ms());
    if (System.currentTimeMillis() < expireDateMs) {
        user.setSubscribedProductId(latestReceiptInfoDTO.getProduct_id());
        user.setPurchaseDateMs(Long.parseLong(latestReceiptInfoDTO.getPurchase_date_ms()));
        user.setExpiresDateMs(Long.parseLong(latestReceiptInfoDTO.getExpires_date_ms()));
        user.setAppleOrderId(latestReceiptInfoDTO.getTransaction_id());
        userRepository.save(user);
        log.info("Subscription processed for user: " + user.getEmail());
        return new UserDTO(user);
    } else {
        log.info("Subscription is already expired, DB was not updated");
        return new UserDTO(user);
    }
} else {
    log.info("Apple API response is null");
    return new UserDTO(user);
}