Hi, the signal into the arduino looks okay, cannot make out the screen graduations too well, but it looks like 5V pulses and they certainly have structure to indicate that it is valid data.
The next step is for you to post a copy of your sketch, so we can see if there are any problems.
By the way, don't be ashamed of your CRO (scope), I'd love to have one like that on my bench, even though I do use digital ones, and as you show it still produces the goods when its needed.
Tom..... 