E gift….empty???

I'm regular user of cash walk and I really enjoy it. I run more than 10miles three times a week,and I'm totally hooked on collecting coins.so far,I've used the rewards three times statbucks and I've been enjoying my marathon club. Today,after my workout,I tried to use the 3of $5 Starbucks rewards I had earned with my friend. After placing my coffee order,I went to pay,but all 3 of E-gift showed up as empty,which really surprised me.since I use an IPHONE,it's not easy to collect 5000coins.....what went wrong???