Hi - you need to report this to Optus so that they can officially investigate this and rectify - the My Optus Instant Messaging works well. We are all customers here, so unfortunately your post will not be actioned by Optus.
If you have tried to Factory Reset the modem by inserting a paperclip into the Reset hole for 10 seconds with power on the modem and you still have a Red flashing LED on DSL or Internet , it implies a problem with the NBN service. The only way you could check if the modem is at fault is to use another modem to do a test or if you have NBN HFC, plug your PC into the Arris modem and see if you have Internet. If you have NBN FTTC, you can do the same test with the white NBN Netcomm unit.
It is also possible that the modem may have done an firmware update.