I cannot download pictures to my mac

If its from google to device, same here then again google sucks, download Firefox browser from google play store for free, its fast and beter for google downloads. If its device to device, its your cord. One or both devices doesnt register the cord or if the cord has high miles the ends get slopy and seem pluged in yet act as not. Id buy a new cord that lists your devices on the package. lastly some files wether video(mp4) or image(mp3) can be incrypted by a device rendering it unreadable exept by the encrypting device. Incrypting is found within your device setings. Some have it in security as its a security measure you can turn on an off with out being an it tech. I hope this helps.