Hi Mishel,
Greetings from Syncfusion.
When using Syncfusion.XlsIO.Portable library in iOS application, the following settings must be done to execute in iOS devices.
Visual Studio:
In Visual Studio, we can only execute in release mode for iOS device by setting the link behavior field to Link SDK assemblies only.
Xamarin Studio (Recommended):
Link behavior: Link SDK assemblies only (otherwise classes you need in Syncfusion.XlsIO.Portable.dll are linked away).
Enable debugging: Unchecked (this is to create a smaller binary, since adding debug information makes it somewhat bigger).
Applying these settings will execute the application properly in iOS device.
You might face the following issues, if the above mentioned build options are missed out.
You might get "Native linking error" while compiling.
You might face runtime Exception ("System.TypeInitializationException").
You can also refer to the ReadMe file for older Xamarin Studio version in the following link.
If the issue still occurs at your end, please share your working version of Syncfusion assemblies along with the issue reproducing sample which will be helpful for us to validate further from our side.
Regards,
Abirami