Just to clarify the situation regarding peer assessment submission.
As it indicates clearly on the login page, you can only submit this task once. However, if you really want to, you can login to the system multiple times as long as you don't click submit. The system will not save your entries so it is best to keep them recorded in a text file if you are intending to login multiple times. Then, before you click submit, just paste your feedback from the file into the form.
Why is the page like this? Because it has been designed as an assessment/hurdle task. You login once, finish the task and submit. I do not encourage you to complete the task in multiple sessions even though this is possible.