I was write to their support, and receive this ansver:
If your Dragon Bones is version 5.6.1, then you could try to close this log in window.
You could save the project and export the project without log in. You could try it.
And if you still can't save the project or export it, please wait a little bit.
we will publish a new version in this week to fix these issues.
Thanks for using our products.