This is not an error. There is a daily limit on how many ads you can watch in Astro Arena.

Once you reach the daily viewing limit, the corresponding "Watch Ad" button will be disabled, and you can use it again after the limit resets. The limit resets at a set time for each ad slot.

If the button remains disabled after trying again later, or if you suspect it is an error, please contact us through the in-game Customer Support menu.