iPhone 4 can't detect any wifi networks after screen replacement

I replaced my iPhone 4 screen and now my iphone wont detect any networks any more.

Although every once in 100 times i start wifi it will detect my wifi and connect fine, i can surf the web but then it dies out.

Checked the EMI shield a dozen times, cleaned all contacts, everything looks good, emi clip is in place, motherboard is located well.

Wifi isnt greyed out, it just wont detect.

Please help.