have you tried to change polarization by default its Vertical try Horizontal

you post antena model but you dont post how long is your pigtail to 5210

this is not TP LINK support this is the TP LINK forum even on top reads Tech Support forum its just TP LINK forum we all help each other. as Knock posted may have to all go back to TP-Link as from...

http://www.tp-link.com/en/article/?faqid=289 i answered your question, but it would be better if you post what you want to do with 5210

first you have to know the ip of your main router, example 192.168.0.1 if the third number is 0 in your router, 0 then you are in same sub-net, its always the third number the one you care for, and...

you posted The setup worked fine (i followed method 2 entering keyphrase and password for my network), Use method 1 Make sure you are in same sub-net as your main router and have latest firmware