“Login timeout” when attempting to connect
Due to an extremely inefficient implementation by Microsoft, some Marketplace skins can use so much bandwidth that they trip PocketMine-MP’s anti-attack security measures.
Try changing your skin to something more conventional, (e.g. Steve, Alex, or a skin imported from an image file) and see if you’re able to connect.
If you’re still not able to connect, the issue may be caused by the server’s plugins.