My BSNL ONT doesn't save username and password

I am having problem with my H640V-G25E ONT Modem which BSNL has provided me, I have configured the modem with PPOE (Always On) connection, But if the modem restarts/shutdown (Due to power fluctuation/cut) then I have to connect my modem once again by entering the BSNL user name & password. Now my question/problem is that if I have configured the connection to always remain on then why after restarting the modem I have to again give my BSNL user name & password in the modem configuration. Is there something wrong with my BSNL modem, Kindly help meI

Also, the power backup UPS that bsnl has provided doesn't work. Should I request for another UPS?

I will be grateful to you if you reply to my query.