Why aren't cards upgraded after watching an ad?

Level up ads give up to 50.000 coins towards a card upgrade

• From the Armory, you can watch ads or use Skip'Its to level up your cards, using the button highlighted in the image below.
• When you watch ads or use Skip'Its to upgrade your cards, you get a maximum of 50.000 coins towards that upgrade.
• If the upgrade costs more than that, the upgrade price will be reduced accordingly. You can pay the remainder using coins or continue watching ads or using Skip'Its until the full price is paid.

You can also see the stages of a card level up by looking at the red/orange lines around the card as you level up