Many of the problems people have with their wifi, especially after a ROM upgrade on their phones is NOT due to a problem with the phone or ROM. Instead, it's due to the phone's wifi protocols being updated to the most current versions and yet their router is still operating on older, outdated protocols.
I would also suggest you go onto your router's manufacturer's website and download the latest firmware for your router, and then install it. Next, power of the router completely. Next, shut down wifi on the phone. Finally, power up the router first, followed by the wifi on the phone once the router is completely back online.
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