Today, i stopped at 4 different pokestops multiple times but couldnt get any pokeballs. My bag is not full but it just spins but not give anything. I am using pokemon trainer club account. We do use the same account on 2 iphones (and both have the same problem).
This is most likely a connection issue. If your connection is bad, or the servers are under heavy load, PokeStops and Gyms will struggle to fully load in, not giving you items.
On a side note, if the PokeStop is staying blue, but saying "Try again later," check your bag, as you probably got the items anyways.
I've had a simular issue lately, but here's what I was able to determine:
If I started Pokemon Go on Data, then moved onto WiFi* (as in coming back home, and getting in wifi range): No issues. (Can see the image of a pokestop and have pokemon spawn nearby.)
If I started Pokemon Go on Wifi, then move onto data* (as walking out of of my house, then driving away): issues with Pokestops that spin but never drop anything, and are missing their location picture. The "loading" Pokeball continually spins as well.
I cannot tell if this issue is a phone or carrier issue, but the fix for this is to terminate/kill the app, then reopen it. Closing the app and leaving it memory will not close the connection. It's that reconnect part which fixes the issue if this is what you're experiencing..
I've had this happen multiple times when there are server issues or I have poor connectivity. Check to make sure you have a good signal or try again later and see if the issue continues.
On a side note this doesn't mean you didn't get anything every time. You can check your journal and it will sometimes show you got the items anyway without them popping up.