Faced Xiaomi redmi note 3 wifi connectivity issue.
It properly connect to wifi hotspot but fails to connect home wifi device.
Enabling/Disabling the router and mobile wifi does not helped much.
What worked for me is the MIUI version upgrade.
Upgraded it to MIUI Global 7.1 (220.127.116.11).
After upgrade, it properly detects and connects to home wifi.
Hope this will help.