2FA OTP Error with Yubikey 5C NFC


I am running vaultwarden with docker compose on gcp.
I have already a FIDO U2F Security Key and a authenticator app set up with no Problem. Now if i want to add YubiKey OTP Security Key i get the following error:
and in the logs:

[2021-05-25 15:08:37.049][request][INFO] PUT /api/two-factor/yubikey
[2021-05-25 15:08:37.113][error][ERROR] Invalid Yubikey OTP provided.
[CAUSE] Network(
reqwest::Error {
kind: Builder,
source: RelativeUrlWithoutBase,
[2021-05-25 15:08:37.115][response][INFO] PUT /api/two-factor/yubikey (activate_yubikey_put) => 400 Bad Request

The Yubikey OTP validates on Yubico demo website

“otp”: “xxxx”,
“nonce”: “xxxxx”,
“sl”: “100”,
“status”: “OK”,
“t”: “2021-05-25T15:07:41Z0214”

and i set the infos in my .env:


Any ideas how i could get i working? Should i open a bug?
When i remove the empty YUBICO_SERVER i get the following in the logs:

[2021-05-25 16:21:18.993][error][ERROR] Invalid Yubikey OTP provided.
[CAUSE] Network(
reqwest::Error {
kind: Request,
url: Url {
scheme: “https”,
username: “”,
password: None,
host: Some(
port: None,
path: “/wsapi/2.0/verify”,
query: Some(
fragment: None,
source: TimedOut,
[2021-05-25 16:21:18.995][response][INFO] PUT /api/two-factor/yubikey (activate_yubikey_put) => 400 Bad Request

These type of auth request need a valid cert and also the domain needs to be configured correctly. Try and verify if that is correct.

Did you have any luck fixing this? I am having the same issue