Your 2FA secret key is not the code you get from the Authenticator app.
This is an activation code you get from LinkedIn once you turn on the 2FA. You can't access it again if you haven’t copied it in your notes when you got it. But worry not, you can reset it easily.
In case you lost your 2FA secret key on LinkedIn, you’ll need to disable 2FA and then turn it back on to get a new key. Be sure to save this new key in a secure location (e.g. your personal notes).
Before you start, remember to select the Authenticator app option. It's LinkedIn's recommended method and the only way to enable HeyReach's Infinite Login.
How to turn 2FA ON or OFF
Install an authenticator app.
Click the profile icon at the top of your LinkedIn homepage and select Settings & Privacy.
Under Sign-in & security, click Two-step Verification to enable or change your verification method.
Click Set up and select Authenticator App as your verification method. You may need to enter your password and verify through either an email code or the LinkedIn app.
Open your authenticator app and tap Add Account or the Add icon in the top right. First-time users may need to complete the initial setup.
Select Other and enter "LinkedIn" as the account name.
Enter the secret key that LinkedIn provides into your authenticator app.
Enter the 6-digit verification code from your authenticator app to verify your device.
IMPORTANT: After re-enabling 2FA, save your new secret key in your personal notes.
