Sessions became a co-sponsor of the Corker bill on 04/15/2015.
The Corker bill put the onus on Congress to muster 67 votes to block the Iran agreement.
The final vote was 98-1 passing Corker’s bill. The bill was sent to house where it passed.
The only Senator to vote no was Tom Cotton. I don’t know which senator was missing from the vote.
decent explanation of Corker’s chicanery.
https://thehill.com/blogs/floor-action/senate/241355-senate-votes-to-approve-Iran-review-bill
This is all very complex; such Congressional ins and outs are very difficult for small brains to comprehend.
I am waiting to find evidence that Sessions voted to pass the iran deal.