API 1.0 unauthorized error

Hi,

We have done Salesforce integration with Clarizen to bring Hours of Task per User, It was working fine till now but now all of a sudden, we have started getting 401 Unauthorized error when we pass the entity Query after fetching the session ID and it says your session has expired though we are making the API call just after fetching the session id

Below is the screen shot.

Can anybody help us with this, why we have started getting this error suddenly.