The problem could be in DHCP lease time unless the ethernet cable was unplugged. DHCP server assigns an IP to Reduxi Controller (or any other network device connected to this DHCP server) for a specific time, for example, 24 or 48 hours.
After 24 or 48 hours, the IP assigned to Reduxi Controller is changed, and you can not access Reduxi Controller over Reduxi Configurator using the old IP.
The solution is to scan again for Reduxi to get the new assigned IP from the DHCP server or to change the new configuration from DHCP to static mode.
Login to Reduxi Configurator, go to Settings -> System -> Network and change from DHCP type to STATIC.
Text description of this image
Screenshot of the Reduxi Configurator (logo: reduxi CONFIGURATOR) in a browser, Network page under System. Browser address bar with a not secure warning icon; the address points to the settings/system/network page; orange badge 1 marks the address bar. Left menu: Users, Devices, Strategies, System (expanded) with sub-entries Identifier, Network (highlighted, orange badge 2), Open VPN, Connector (+), Configuration (+); buttons + Add device and + Add strategy; entries Settings and Profile. Main area titled Network, table: Ethernet IP: 192.168.1.99; Ethernet Netmask: 255.255.255.0; Wireless IP: empty; Wireless Netmask: empty; Mobile IP: empty; Mobile Netmask: empty; Proxy: empty; Default route: 192.168.1.1 (192.168.1.99); Active connection: Wired; Internet connection: green check mark. Section Settings with tabs: Wired network (selected), Wireless network, Mobile network, Proxy server, Network redundancy. Field Type: DHCP, marked by orange badge 3.