Not sure what's wrong, they're both supposed to have bluetooth 4.0. I've tried turning bluetooth on/off, turning the speaker on/off, and resetting the phone. I removed all other bluetooth pairings and devices. The speaker pairs with an iPhone 5s ok, but the 4s doesn't seem to see it. The 4s works ok with a bluetooth headset, so it doesn't seem to be that, either. I didn't find any other discussions about this, has anyone else had a similar issue?