can not connect to airport to back up my files does not recognise password
Time Capsule not recognising password to connect with the system
Time Capsule 802.11n (3rd Gen), iOS 9.2
Try to retrieve the password using AirPort Utility on your Mac.
Open AirPort Utility (Finder > Applications > Utilities > AirPort Utility)
Click on the picture of the Time Capsule
Click Edit in the smaller window that appears
Click the Base Station menu at the top of the screen up where the File, Window, Help menus are located
Click Show Passwords
If this is not successful, then you will have to reset the password again.
Study the information in this Apple support document about a Soft Reset.