Hello, welcome to phpBB.
Do you have any kind of documentation for ‘Core identity server 4‘ pertinent to your request? I doubt many users here have much experience with it as it’s ASP.NET but you never know. If you get no joy here you could try a support site specifically for your server or you could try the custom coding forum but more information will be needed.
"The more connected we get the more alone we become" - Kyle Broflovski©