To troubleshoot this issue please head to Settings > Connections > Wi-Fi > Tap the cog symbol to the right of your router > Forget > Back > Toggle Wi-Fi off and on again > Select your router from the list of available connections, and run through the connection steps. Now, tap the 3 dots in the top right corner > Advanced > Wi-Fi Control History > Check if any apps have recently disabled your Wi-Fi. If this is the case, head to Settings > Apps > Select the relevant app > Permissions, and disable any Wi-Fi related permissions. If the issue persists, please try pressing the Volume Down and Power buttons together for around 10 seconds until the phone restarts, as this will refresh the software and address any issues that might be a contributing factor. I'd also recommend unplugging your router at the wall for around 30 seconds, then plugging it back in to force a reset. I hope this helps.
