Q:

Not logged in at Pluralsight

I was able to get a Pluralsight assignment before and I was successfully logged in with my Stack Overflow linked account.  But now it doesn't work anymore. 
Clicking "Get your Skill IQ" on Stack Overflow Jobs leads to https://stackoverflow.com/users/story/integration/assessment?s=1, which forwards to https://www.pluralsight.com/partners/stack-overflow/iq?aid=[ID]&promo=&oid=[ID]&utm_source=&utm_medium=partner_partner_web_referral&utm_campaign=&utm_content=&utm_term=.
I only censored the "aid" and "oid" variables, because I don't know what they are.  The other variables are actually empty and the & in the link follows directly after the = of the previous variable.  I don't know if that's intended. 
The result is the same as just opening pluralsight.com/partners/stack-overflow. 

A:

When you are redirected to Pluralsight, you need to log in there and find the result you want to share with your developer story. 
Once you do, open it and you should use the Stack Overflow icon to share it back. 

Once you click it, you should be redirected to your dev story where you can confirm that you want it there.