Exported game crashes but works in editor

Godot Version

v3.5.3.stable.mono.official

Question

Hello! I’ve got a game made in Godot 3.5.3 and written with GDScript. It works at all… I would like to port it in Godot 3.5.3 mono because I would like to add some functions related to the EOS (Epic online services) available only via an asset requires c# version of Godot.
I’ve loaded the code in Godot v3.5.3.stable.mono.official and converted it to C# via editor command (Project->Tools->C#…) and still works well in editor, but I’m not able to export. When I try to lauch exported version, I get this log:

Mono: Initializing module...
Mono JIT compiler version 6.12.0 ((no/6051b710)
Mono: Log file is: 'C:/Users/gianl/AppData/Roaming/Godot/app_userdata/Test_00/mono/mono_logs/2024-05-10_08.10.15_4516.log'
Mono: Runtime initialized
Mono: Loading assembly mscorlib...
Mono: Assembly mscorlib loaded from path: .mono/assemblies/Release/mscorlib.dll
Mono: Loading scripts domain...
Mono: Creating domain 'GodotEngine.Domain.Scripts'...
Mono: INITIALIZED
Mono: Loading assembly GodotSharp...
Mono: Failed to load Core API assembly
ERROR: Failed to load one of the API assemblies.
   at: _load_api_assemblies (modules/mono/mono_gd/gd_mono.cpp:969) - FATAL: Method failed.

Does anybody know what’s the problem, please?

By the way: I tryed a really simple test project create from scratch with v3.5.3.stable.mono.official with same results…

Founded the solution to this problem! Simply, the main class of your project needs a C# script attached to it!