Ad blockers prevent Joko from tracking your purchases and, therefore, from earning money. Therefore, to earn cashback, you must disable all your ad blockers.
On Google Chrome :
Go to "More tools" > "Extensions", by clicking on the 3 dots at the top right of your Chrome window
In the list of your extensions, deactivate the extensions that block ads: Adblock, Adblock Plus, Adblock Premium, Avast Online Security...
On Mozilla Firefox :
Go to "Add-ons" > "Extensions", by clicking on the 3 bars at the top right of your Firefox window
In the list of your extensions, deactivate the extensions that block ads: Adblock, Adblock Plus, Adblock Premium, Avast Online Security...
On Safari :
Go to "Preferences" > "Extensions", by clicking on "Safari" at the top left of your screen
In the list of your extensions, deactivate the extensions that block ads: Adblock, Adblock Plus, Adblock Premium, Avast Online Security...