Message: Collection not found

While writing an internal using the Qt

Error transferring http://uscogdb-v001.i.hmnc.us/v1/databases/hpprx-drug-pricing/collections/6610f0d1003d0ae4b426/documents - server replied: Internal Server Error, {"message":"Server Error","code":500,"type":"general_unknown","version":"1.5.4"}

Following the AppWrite log gives me this,

[Error] URL: /v1/databases/:databaseId/collections/:collectionId/documents [Error] Type: Utopia\Database\Exception [Error] Message: Collection not found [Error] File: /usr/src/code/vendor/utopia-php/database/src/Database/Database.php [Error] Line: 2623

I'm attempting to perform the following-

TypeScript

/** ...Header snip... **/
Dialog::Dialog(QWidget *parent)
    : QDialog(parent)
    , ui(new Ui::Dialog)
    , error(new QErrorMessage(this))
{
    connect(ui->cmdSyncData, &QPushButton::clicked, this, [=]() {
        AWDatabasesApi api;
        QEventLoop loop;

        api.setApiKey("drug-import", queryAPIKey());
        api.setNewServerForAllOperations(QUrl("http://uscogdb-v001.i.hmnc.us/v1"));
        
        ui->cmdSyncData->setEnabled(false);
        
        connect(&api, &AWDatabasesApi::databasesListDocumentsSignalE, this, [&](AWDocumentList, QNetworkReply::NetworkError, QString err) {
            ui->cmdSyncData->setEnabled(true);
            qDebug() << "Error.";
            error->showMessage(err);
            loop.quit();
        });

        api.databasesListDocuments("hpprx-drug-pricing", "6610f0d1003d0ae4b426");
        QTimer::singleShot(5000, &loop, &QEventLoop::quit);

        loop.exec();
    });
}

QString Dialog::queryApiKey() {
    return "api-key";       
}

TL;DR

Developer forgot to enable `Document Security` in settings and set permissions for collection. Additionally, set “X-Appwrite-Project” in headers. Server error with message "Collection not found" was due to a missing setting.