Netgear Omnidirectional MIMO Antenna For 3G/4G/5G Mobile Modems and Hotspots

Hi,
I purchased one of these hoping to supplement the signal on my Nighthawk M6 but I find that although it enhances 4G reception it doesn't really help with the 5G frequencies, if anything it seems to make them worse.
Just wondered if anyone else has any experiences with this product?