Wifi connectivity issue

Plz check after reset your network settings in setting tab.

Is the router dual band?
If that's the case then this may be due to the router's preference of 5Ghz connectivity to your phone over long range 2Ghz or 2.5 GHz connectivity.
This will happen if the router detects a heavy traffic in 2GHz band, or if 5GHz is preferred over 2 for supported devices.

Dear Samsung Member,

Greetings from Samsung Customer Support!

Please perform the below mentioned steps to resolve the issue:

* Forget the Network: Go to apps screen >Settings >Connections > Wi-Fi >Wi-Fi network >Tap and hold the Wi-Fi network that you're having trouble with until the menu allows you to select Forget Network.

For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).

Thank you for writing to Samsung.

Warm Regards,
Samsung Customer Support