The password to open ITR-V (acknowledgement) is combination of PAN (in lower case) and Date of Birth in ddmmyyyy format.
For example, if the PAN is AAAPA1111A and Date of Birth is 28/12/1986, the password should be entered as aaapa1111a28121986
In case you are still unable to open the acknowledgement with your password, then please call on any of below numbers:
Aaykar Sampark Kendra (ASK) - 18001801961 or 1961 (Monday to Saturday from 8 am to 8 pm)
E-filing Unit - 1800 103 0025 (or) +91-80-46122000 (Monday to Saturday from 9 am to 8 pm)