You can refer to this forun post : https://community.tp-link.com/en/business/forum/topic/150177?replyId=300727

Just to close the loop on this, I never found an answer as to why this was occuring.  I went through the above post and tried everything in there along with many other things I found elsewhere and could never get speeds on the 5 gHz band to be anywhere near what the ISP's modem provided, so I ended up returning the EAP 225.  

Hi, I do not know if you are a network technician, but you should have checked the port of the ISP router you wired the eap to, it's surely a 100Mbps port, not a giga bit Port. If I am right, you won't get more than 100Mbps