why doesnt my imac pick up my iphone pictures

Before the last update, when I would plug my Iphone 6 plus into my IMac, It would automatically bring up my Iphotos and ready to upload all photos off my iphone. Now I cant get it to come up and when bringing my iphoto up, its not asking me to upload. How can I get Iphoto to do this again as I want to put photos to my hard drive on IMac and get them off my Iphone?