NYC | Uber Store Delivery

Hi guys, long story short I used uber to order some dog food, my driver drove for about 30 min. I'm trying to tip but the app isn't letting me. Luckily have an android and can look at my notification history. I have the notification which ask me if I'd like to tip, but I click it and it shows me a shopping bag, and refer a friend.

I feel so bad I wanted to tip this person but the app isn't letting me. Is there just a delay or am I missing something?

Looking for guidance from NYC Uber drivers, or users in the area. I don't want this person to go untipped. Any help is appreciated.