'Not setup as worker' error even though 'Person' is attached to FND User

Hi,

We are on 12.1.3. I am getting the 'Not setup as worker' error when I try to open the Requisitions or Purchase orders forms. I have defined several users and have attached an employee (Person) to each user. I also have defined some Employees as Buyers. Every user who has an employee (Person) associated to his FND User record was able to access Requisitions form and every employee who is defined as a buyer was able to access the Purchase Orders form till yesterday. 

But today all those users are getting aforementioned error message. I was wondering if anyone has faced such problem earlier and can help with possible solution. I could see some patches applied yesterday in the ad_bugs table.