Since getting my S20 Ultra I have had an issue where if I connect to my home network wifi, and then leave the connection range for awhile then come back, my phone will not be able to reconnect to the wifi. It will simply give me a can't authenticate the connection error over and over. If I restart the phone it always connects back with no issue until I leave range again. This hasn't been an issue with my previous phones and my room mate has no issue with his Apple phone, so does anyone have any suggestions as to what might be causing this?
I have the same issue with my S20 Ultra. If I leave the range of the router and reconnect, it connects at a very slow speed or shows no internet connectivity. This was also an issue for me with S10 and S9. Apple phones don't do it or other Android phones.
If you go to Settings > Connections > Wi-Fi > Tap the cog symbol to the right of your router, is Auto Re-connect enabled? if you tap on 'Advanced' and try adjusting your IP, Proxy and Metered Network settings, do you notice an improvement?
Can you also try going to Settings > Connections > Wi-Fi > Tap the 3 dots in the top right > Advanced > Switch to Mobile Data > Off > Turn On Wi-Fi Automatically > On > Wi-Fi Power Saving Mode > Off, to see if this helps?
Although it isn't ideal, if the issue persists I recommend manually disabling Wi-Fi via the Quick Panel when you're planning on moving out of range, then manually re-enabling it when you're back in range. Also, disable Mobile Data when you are back in range of your router, to avoid any connectivity conflicts.