weak security (WPA)

Apple devices will show a weak security warning if your router security settings are not set to WPA3 or WPA2 AES. How you change those settings varies by router. If you don't have instructions, do an internet search for your router brand/model or if your router is supplied by your Internet service provider, check their website or customer support. Also see: Recommended settings for Wi-Fi routers and access points - Apple Support