Can't connect to 5Ghz

I am using a Netgear WNDR3700 V4 Router running the latest build of DD-WRT and I cannot connect to it on 5Ghz using the Minix Neo X8 H Plus.

The Minix sees the 2.4Ghz and 5Ghz signals coming from the router but will only connect to the 2.4Ghz option.

I recall using the 5Ghz a while ago and it worked fine, my ancient Thinkpad laptop connects to the router on 5Ghz perfectly.