feat(troubleshooting): add gpg and ssh troubleshooting section

README.md

@@ -195,8 +195,26 @@ This creates the file `id_ed25519_sk-keyring-cert.pub` that is the certificate t
 
 ---
 
-# x509
+# Troubleshooting
+## GPG
+Sometimes, for unknown (for me) reason, you need to kill the gpg-agent to be able to use the YubiKey again. 
+```bash
+gpgconf --kill gpg-agent
+```
 
-## Master Yubikey
-I create a certificate in PIV slot 9a with Yubico authentificator. This CA would be use as a Root CA for my server.
-TODO fix with XCA
+You also sometimes need to restart the pcscd service if the YubiKey is not detected.
+```bash
+sudo systemctl restart pcscd
+```
+
+## SSH 
+If you have an issue with your gpg-agent, you maybe have to wake up the ssh-agent to be able to use the YubiKey again. 
+This basic commande wake up the ssh-agent.
+```bash
+eval $(ssh-agent) # Should response with "Agent pid [number]"
+```
+
+If your key is not found by the ssh agent, you have to manually add the key with:
+```bash
+ssh-add ~/.ssh/id_ed25519_sk-keyring
+```