Is it possible you are entering it incorrectly? Maybe you got a “sticky” key. Try copying the password from the admin panel & pasting it in directly.
Also make sure to turn off “Private address” in the Wi-Fi options on iOS. It has caused some issues in the past for me.
If it still doesn’t work, you could try the beta firmware. I don’t know if this issue was reported before, or a known issue, but it’s possible it got a (silent) fix.
You can download beta’s from here, mind you they might be unstable.
https://dl.gl-inet.com/