Hello,
I believe you might be hitting the same bug in the post here: CentOS host cannot subscribe to repositories
First, run this command on your Foreman server:
sudo su - postgres -c "psql -d candlepin -c \"select id,enddate from cp_pool where enddate > '2049-12-31 00:00:00';\""
If it returns any rows, then you are hitting that bug. To fix, upgrade to Katello 3.14.1 and follow these instructions: CentOS host cannot subscribe to repositories
Let us know if you have any other questions.