Depending on the browser, there are different ways to reset it. You will find instructions here for:

It involves two steps.
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First: In case you are already subscribed to push notification for your store, you would need to first reset notification permission by clicking on the lock icon.

Set the Notification Permission to "Ask (default)"

The second step is to clear your browser cache.
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​Right click anywhere on the page > Inspect > Application  to see the following option:
An example screenshot to clear the cache on Chrome is:

The above instructions will reset your browser for push notifications.