Expression error

Can you give more context like what is the scenario and when the error came. Also if possible, share related code snippet for better support.

I was getting this error when i open a task. i was able to open the interface from the process model 

thammireddybinduniharika said:

when i open a task

What exactly do you mean by that? From where?

this was the error when i open one of the task from the admin dash board 

I suggest you to find the process instance which has this error in the process monitoring tab. Then investigate the underlying interface if with test inputs its working fine or not. The error relates to querying data so check any variable or component that is involved in a data query to identify which one is failing and causing this error. Once you have identified the root cause then we can move towards finding ways to resolve it. So check from your end and share what you find to help us help you better! 

in the instance i was able to open the task

What is the current situation? Are you able to access task from front end properly or in the front end there is consistently some error?

Grant the user proper record-level security or data store permissions for whatever data the interface queries.​​​​​​​​​​​​​​​​

I can reproduce this and I believe it is a product bug.  I will be opening a support case for it later.

The conditions seem to be as follows:

1) a task is assigned and accepted, still outstanding

2) I, as a system admin (and presumably any other user with viewership permissions on the task instance), can open the task fine from the Process Instance Monitor, but if I try to open the task within a SAIL form via a standard task link, I get an error identical to the one you describe in your post and subsequent screenshots.

turns out it's a product bug and is already being tracked by Appian.