Maybe you have the same issue as I do (https://forums.dolphin-emu.org/Thread-wii-wii-sports-resort?pid=322211#pid322211 ). A workaround is plugging in the Nunchuk, too. (Then you might have to unplug and re-plug the motion+ and/or press F5 to disconnect and press it again to get it to reconnect again)
Intel i5-4690k (Devil's Canyon) @ 3.5 GHz (+Scythe Mugen) / Gainward GTX 1070 Phoenix (OC'd) / ASUS Z97 PRO GAMER / 16GB G.Skill DDR3-2400 CL10 TridentX / X-Fi XtremeMusic / Win10 Pro 64bit / Dell S2716DG Monitor / 3x original WiiMote+MotionPlus+Nunchuk