Other people were reporting this issue on the KI Discord yesterday, and I shut my PC down last night and rebooted this morning to encounter the same issue.
It gives error 0x87DD0005, saying it cannot sign into my XBox Live account. However, I can sign into the XBox app just fine. Other people are reporting they can play other games, and this issue is unique to KI. Though I am on Windows 10, some of the people reporting the issue are using the XBox.
@KRAKENJIMMY or other devs, please help! Some server probably just needs a reboot.
Thanks in advance for your help.