CAPE CANAVERAL, Fla.—Spacewalking astronauts encountered cable trouble Wednesday while attempting to make improvements to the International Space Station’s European lab. Only one of the two lab upgrades was completely successful. NASA’s Mike Hopkins and Victor Glover installed a new antenna on Columbus, one of three high-tech labs at the orbiting outpost. It took a few tries by scientists in Europe to get it turned on properly. No longer needed, the boxy antenna cover was thrown overboard. “Here we go. Countdown: 3-2-1,” Glover radioed as he heaved it safely away from the space station. Elsewhere on the lab, Glover could not hook up all the power and data cables on a science research platform that’s been awaiting activation for almost a year. He managed to hook up four of six cables. They checked out well with power flowing, enabling partial use of the platform. But connectors on two cables would not …