I have a database with Yubikey 2FA Challenge-Response enabled.
If I remove the yubikey from the USB port and re-insert it, then saving the database fails with

Writing the database failed.
Unable to issue challenge-response.

This error also occurs, after the OS woke up from the suspend-to-ram state.

Expected Behavior

Database is always saved

Current Behavior

Database is only saved, when Yubikey has never been removed before.

Possible Solution

Scan for Yubikey before Saving Database

Steps to Reproduce (for bugs)

1. Create a database and enable Challenge-Response with Yubikey inserted
2. Add entry
3. Save database --> success
4. Remove Yubikey from USB port
5. Add entry
6. Re-Insert Yubikey to USB port
7. Save database

Result: Error

Writing the database failed.
Unable to issue challenge-response.

Workaround

1. ...
2. ...
3. ...
4. ...
5. ...
6. Re-Insert Yubikey to USB port
7. Open "Change master key" dialog
8. Activate "Challenge Response" checkbox
9. Cancel "Change master key" dialog
10. Save database

Context

Build: -DWITH_XC_YUBIKEY=ON

Your Environment

Debian Linux Jessie
KeePassXC - Version 2.1.4
Revision: ad79162

Libraries:

• Qt 5.3.2
• libgcrypt 1.6.3

Enabled extensions:

• KeePassHTTP
• Auto-Type
• YubiKey