Yubico Authenticator stopped working suddenly

[Zetamex]

Been using Yubico Authenticator app for years since PayPal started requiring 2FA. Two weeks ago the first code from the app stopped working and I had to wait for the second key, which worked. As of two days ago the keys stopped working entirely. Today I removed 2FA from the account and tried adding the app again, but PayPal reports the code as bad and won't accept it. I just used Yubico to auth with GitHub so it's not the key itself that is broken. Updated the app to the latest version and tried manually adding via the secret, all to no avail. After contacting customer support setup Google auth app instead, which works fine. Removed that again and tried adding the Yubico again and still failing, no matter how long I wait before trying a code.

This seems to be on PayPal end of things as it started slowly and it works fine with GitHub. Escalating through support to see if someone might know, but was encouraged to post here as well. Couldn't find any mention of issues directly with the app only vaguely related Yubikey things that were left unanswered or with boilerplate responses.

Using Yubico Authenticator version 6.2.0 with a Yubikey 5C

[Zetamex · Accepted solution]

Received a reply from Yubico with some instructions to change the ntp server to a different one in order to force a proper time update. After searching for why this might be necessary also stumbled upon the information that Windows only does a time update once per week, which seems rather bad if time drifts by multiple seconds. Evidently there is a registry key that holds the interval time, which can be changed to something more reasonable like once a day. I'm not sure why time started drifting by more than a minute, but not sure how to investigate that.

I was able to add the Yubico Authenticator back to my account now. Before contacting support I did not have the option to deactivate 2FA, support did that and since then I am able to do this myself. Not sure why that is.

Hopefully this helps as reference, check your time and sync it or change the interval.