same issue on iphone 15 pro max(iOS 18.1),also can connect the same wifi whith iphone13。why？

we are facing the same issue on iOS18.1 in our app to connect our loT . In some case iPhone 13 working well with the same WiFi-network,and the new devices some like iphone 15 pro max/iphone 16 with new os version can not connect. The issue seems to be growing on new systems recently. We have recently received a lot of user feedback regarding similar issues, but as developers, we are unsure what is happening. The error is nil. What can we do for our app users?

FB16057509 (iOS18.1 unable to join network) .I had upload the wifi log and system log. This is the feedBack ID.