Sorry to hear you're having some issues with the Optus Sport app on your Fetch TV.
I would first suggest completing a soft reset of your device and if that doesn't work, then perform a hard reset of the Fetch TV box.
You can find out how to do this on our How to reset your Fetch box on our support page.
If you’re still needing a hand, we recommend messaging us via the My Optus App. The team is available 24/7 and are ready to assist customers as quickly as possible.
If for some reason you’re unable to, if you have a social media account, please then send a PM to Optus on Facebook or a DM on Twitter with the details for further assistance mentioning you’re unable to use the My Optus app.