Reason 2

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by Karakrull

by Karakrull

                                        
                                                  If you have all 4 keys🟨🟥🟦🟩, and still the door won't let you in. It could be that it is a real bug.

Honkai Star Rail has a good service if you complain about bugs and that's because it's a very newly game so they are willing to correct the errors.

Write to them at (hsrcs_en@hoyoverse.com) they should answer you in 24 hours approx. Remember to add screenshots (of the cards you have, and of the door denying you entry) and describe the problem clearly.