If your Samsung Galaxy S5 may not find or be able to connect to a specific 5Ghz wireless network, you may want to check which channel the network is operating on. The S5 has problems when trying to connect to DFS-channels (Dynamic Frequency Selection).

DFS-channels are basically every channel from channel 52 and up. Try setting your AP to a channel between 36-48 (inc.), and then try reconnecting your S5.