Hi all
First of all, there are Program managers to approve the JSL request form (infopath form) and they used to open the infopath form through sharepoint site (worklist).
Issue here is, One of the PM is not able to access the sharepoint site and he is able to see the worklist item. If he tries to open to approve, he is not getting the infopath form open. Instead he is getting error.  

The page cannot be found.  Http 400 bad request. 

1. Intially he was not able to view the sharepoint site. I fixed through the internet explorer tool.
2. His account is in AD account. Checked his rights permissions. (gave control level in sharepoint site)

Please let me know what else I have to check and do?

 Thanks

Ravi