Totally normal! This happens because our servers connect to your account from a new location/device. Very similar to when you first sign in to Linkedin from your phone or a new computer. You'll receive a pin code to your email, which you then just paste into our dashboard when it asks you.
Note - you only have 1 minute to do this, after which the code becomes invalid and Linkedin will send you a new one.
Open your browser and login to linkedin.com
Right click anywhere on the linkedin.com website -> select 'Inspect' -> Application
Scroll down, to find the cookie named li_at and copy the value of that cookie. Please make sure you copy the whole value of the li_at cookie.