Ibotta app errors

[ConnieR]

Hi, I just got a Samsung Galaxy s4 Mini. It's a definite upgrade from the cheap unlocked phones I usually get. But I have one issue, and I can't figure out if it's the app or the phone. My most important app is Ibotta, which gives cash back for grocery purchases. I can unlock rebates, and upload receipts to other stores, but not Walmart. Every time I try to upload a Walmart receipt, I get a "Reload" error (basically just a white circle with Reload in the middle of it). It works fine on my Straight Talk Alcatel A520L, which is a really cheap phone that Ibotta's not even supposed to be compatible with. Both phones are running Android 4.4, and neither are rooted. Does anyone have any idea what could possibly be causing this error, and any way to try to fix it? Ibotta's support is pretty useless.