Metadata Store Key was changed so that it is not compatible with 2.7.1.

The code is in org.apache.dubbo.metadata.identifier.MetadataIdentifier
this.side = url.getParameter(SIDE_KEY);
        setApplication(url.getParameter(APPLICATION_KEY));
    }
    public String getUniqueKey(KeyTypeEnum keyType) {
        if (keyType == KeyTypeEnum.PATH) {
            return getFilePathKey() + PATH_SEPARATOR + DEFAULT_PATH_TAG;
        }
        return getIdentifierKey() + META_DATA_STORE_TAG;
    }
    public String getIdentifierKey() {
        return serviceInterface + SEPARATOR + (version == null ? "" : version + SEPARATOR) + (group == null ? "" : group + SEPARATOR) + side + SEPARATOR + application;
    }
    private String getFilePathKey() {
        return getFilePathKey(DEFAULT_PATH_TAG);
    }
    private String getFilePathKey(String pathTag) {
        return pathTag + PATH_SEPARATOR + toServicePath() + PATH_SEPARATOR + (version == null ? "" : (version + PATH_SEPARATOR))
                + (group == null ? "" : (group + PATH_SEPARATOR)) + side + PATH_SEPARATOR + getApplication();
    }
    private String toServicePath() {
        if (ANY_VALUE.equals(serviceInterface)) {
            return "";
        }
        return URL.encode(serviceInterface);
    }
    public String getServiceInterface() {
        return serviceInterface;
    }
    public void setServiceInterface(String serviceInterface) {
        this.serviceInterface = serviceInterface;