IP Office certificate date(s) are invalid

Try this:  https://support.avaya.com/forums/showthread.php?t=4850

1) Use ipo manager to communicate without certificate

File > Preferences >security > Manager certificates Check > to None

2) Default the security settings which creates another unique, self-signed instance
with same name but differing instance.

3) Security settings > system > identity certificate > delete the certificate and save security configuration ipo will generate a new self signed certificate.