@Sheikh7777 

 

Hi,

 

What you describe sounds to me like the iPhones' trying to conserve battery power to extend battery life. Basically a battery optimization feature. 

If we do a Google search for "iphone wifi disconnects when locked" there are plenty of search results about these issues and a large number of places showing potential "fixes" for those issues.
Commonly mentioned things for iOS are, "Forget" the Wi-Fi network and then reconnect again, turn off "Wi-Fi Assist", perform a "Reset Network Settings".

Going by the user comments under those articles, forum theads or YT videos the mentioned "fixes" occasionally appear to work for some people, while you will find many other people commenting that the fixes don't work for them.

 

I’ve tried everything which is available on internet I’ve reset network multiple times I’ve reset and upgrade firmware on router as well It works perfectly fine when I’m on it But as soon I lock or phone goes sleep mode I can see on tp link app the device disappear then will re appear after few minutes if anyone is calling me I don’t get it or iMessages until I unlock it Now last option I’m gona try is to restore iPhones and see how it is