Error on dropdown or combo

Job ID: 35026861

Budget: $10 – $30 USD

Hi, I use ASP. NET .NET Framework 4.8
It has 2 combo parent and child

Every time combo value change in parent, child is refreshed use ajax

but something weird happen, when I use button_click value in combo can't change, it just show value in first time we init the combo.

Anyone can fix it please bid, i can show the error
Related categories: .NET C# Programming HTML ASP.NET Microsoft SQL Server