In order for your odds preference to save, you must be logged in when changing your odds preferences.
On a PC/Laptop:
Go to Sports across the top banner of the website.
Scroll down to the bottom of the left access options
You will see 'Odds format': 'FRACTIONAL' or 'DECIMAL', select the format to change the odds.
On a mobile:
Click on the A-Z Sports menu (bottom navigation) and this will display the Sports list.
Scroll to the bottom of the menu and you will see
'Odds Type': 'FRACTIONAL' OR 'DECIMAL' - Clicking on either of them will allow you to change.
We are currently aware of an issue where your selected odds preferences do not save for some of customers. We are looking at this as a priority and will have this resolved for you shortly.