QML module not found in Designer using QML_ELEMENT

[Oleg R.]

Hello,

I integrated C++ class into QML using QML_ELEMENT. While it compiles and works find, in Qt Designer, in QML file the import line with module name is highlighted and error appears: QML module not found (Backend).

In .pro file I have the following:

CONFIG += qmltypes

QML_IMPORT_NAME = Backend
QML_IMPORT_MAJOR_VERSION = 1

In apimanager.h file I have the following:

class ApiManager : public QObject
{
    Q_OBJECT

    QML_ELEMENT

    const QString apiUrl = "https://127.0.0.1:8000/api/";

public:
    explicit ApiManager(QObject *parent = nullptr);

    Q_INVOKABLE void login(QString username, QString password);

I'm running Qt 5.15.1 on MacOS. While having the same version on my Laptop does not show this error, on my Desktop PC it does. I have tried to fully reinstall Qt (manually deleted all config and cache folders).