The last couple of days I have experienced extremely slow NBN internet, something I haven't had an issue with in the past. My mobile internet has no problems and it's with the same company.
I've tried all the suggestions and nothing is working
worth checking if there is an outage in your area. what type of internet service do you have? how are things connected etc. If it is not an outage then I could be anything from modem, nbn, cable, devices, enviroment, windows update...etc. Please provide more information about the issue that you are having, your setup, internet type and troubleshooting steps taken so far, etc.
Mobile Phones and NBN are completely different infrastructures (its like saying my electricity is out but the gas is working)
Are you testing the NBN over a wired connection or wifi? Try wired.
Alternatively contact Optus and ask them to check your line from their end. They can confirm a NBN issue and will be the ones to arrange a fix if needed. As mentioned an outage / wider issue could also be at play.