Lack of recognition of the system.text.json in Rhino 8."

I am developing a Grasshopper plugin in Rhino 7 and 8. In this plugin, I have used a system.text.json file that works perfectly in Rhino 7 without any issues, but I encounter the following error in Rhino 8.I am using version system.text.json 8.0.3. The only solution I found is setting the runtime to .NET Framework in Rhino 8. I am sure about copying the DLL next to the plugin file.

Message=Could not load file or assembly ‘System.Text.Json, Version=, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51’. Could not find or load a specific file. (0x80131621)