Firebase TestLab XCTest Succeed, but no screenshoots

Question

I run a XCTest (UI Test) via Firebase TestLab, it's succeed。But no screenshoot

In the case, I make a attachment via "XCTAttachment"

- (void)testHomeButton {
    XCUIApplication *app = [[XCUIApplication alloc] init];
    [app launch];
    
    // click button2
    XCUIElement *button2 = app.buttons[@"button2"];
    [button2 tap];
    
    // get button2 screenshoot
    XCTAttachment *attachment1 = [XCTAttachment attachmentWithScreenshot:XCUIScreen.mainScreen.screenshot];
    attachment1.name = @"button2 Screen";
    attachment1.lifetime = XCTAttachmentLifetimeKeepAlways;
    [self addAttachment:attachment1];
    
    // click button3
    XCUIElement *button3 = app.buttons[@"button3"];
    [button3 tap];
    
    // get button3 screenshoot
    XCTAttachment *attachment2 = [XCTAttachment attachmentWithScreenshot:XCUIScreen.mainScreen.screenshot];
    attachment2.name = @"button3 Screen";
    attachment2.lifetime = XCTAttachmentLifetimeKeepAlways;
    [self addAttachment:attachment2];
    
    // click testview
    XCUIElement *testview = [app.otherElements.element childrenMatchingType:XCUIElementTypeAny][@"testvc_view"];
    [testview tap];
}

I have got screenshoot successfully via xcode test (command + U) xcode test result

However the test result of firebase has no screenshoot attachments, only contains logs and videos

What should I do to get the screenshot？

Thanks a lot!