I have got multiple connection problems with iPhones and Zyxel t-54.
Around 5 months ago we have purchased 1000 mb/s fiber optic internet with Zyxel t-54 router for wi-fi connection. Everything was working perfectly for the first few months until the new year (2023) , unfortunately, after one week into new year, our wi-fi started to show problems.
The problem is that iPhones are often disconnected from wi-fi, or do not receive internet from it, now the problem has increased as devices cannot connect to wi-fi at all (when you try, it shows that the password is incorrect, even though it's correct). The problem only occurs with iPhone devices, and additionally, every iPhone shows that the wi-fi has low security (WPA/ WPA2), but I have checked and the router has WPA3 personal standards which are ideal for iPhones.
I tried everything: restarting the router, disconnecting the plug, restarting iPhones, clearing network settings and memory on iPhones, etc. Sooner or later e verything failed, I also tried to look for an answer in the admin setting of the router/ internet and observed that even though iPhone is connected to wi-fi, you cannot see this device among connected devices. From time to time they appeared but not a lot of time had to pass till you couldn't see them. Additionally, I have contacted Apple customer service multiple times and tried rebooting the phone, have done a diagnosis etc. and everything showed the same result- no problem with iPhone.
Is there any solution to this problem if it becomes unbearable? Can someone help?