Xamarin iOS won't connect to Rest API from a Simulator - xamarin

Question

I have a Xamarin iOS app that connects to an API (written by me). Sometimes I suffer from a problem where the Simulators (running on Windows 10) will not connect to the API. Whereas the same code runs fine on an iPhone connected to the MAC on my network.
It throws the following exception:
{System.Net.Http.HttpRequestException: An SSL error has occurred and a secure connection to the server cannot be made.
---> Foundation.NSErrorException: Error Domain=NSURLErrorDomain Code=-1200
"An SSL error has occurred and a secure connection to the server cannot be made."
UserInfo={NSErrorFailingURLStringKey=https://api.staging.MyApp.com/api/v1/LogOn/,
NSLocalizedRecoverySuggestion=Would you like to connect to the server anyway?,
_kCFStreamErrorDomainKey=3,
_NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <61E93B00-972D-4DF1-BA39-0141116988C2>.<1>,
_NSURLErrorRelatedURLSessionTaskErrorKey=(\n "LocalDataTask <61E93B00-972D-4DF1-BA39-0141116988C2>.<1>"\n),
NSLocalizedDescription=An SSL error has occurred and a secure connection to the server cannot be made.,
NSErrorFailingURLKey=https://api.staging.MyApp.com/api/v1/LogOn/,
NSUnderlyingError=0x600001cac840 {Error Domain=kCFErrorDomainCFNetwork Code=-1200 "(null)" UserInfo={_kCFStreamPropertySSLClientCertificateState=0,
_kCFNetworkCFStreamSSLErrorOriginalValue=-9816,
_kCFStreamErrorDomainKey=3,
_kCFStreamErrorCodeKey=-9816}},
_kCFStreamErrorCodeKey=-9816}\n
--- End of inner exception stack trace ---\n
at System.Net.Http.NSUrlSessionHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) [0x001d4] in /Library/Frameworks/Xamarin.iOS.framework/Versions/13.18.2.1/src/Xamarin.iOS/Foundation/NSUrlSessionHandler.cs:523 \n
at System.Net.Http.HttpClient.FinishSendAsyncBuffered (System.Threading.Tasks.Task`1[TResult] sendTask,
System.Net.Http.HttpRequestMessage request, System.Threading.CancellationTokenSource cts,
System.Boolean disposeCts) [0x0017e] in
/Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/external/corefx/src/System.Net.Http/src/System/Net/Http/HttpClient.cs:506 \n at MyApp.Mobile.Api.LogOnUser (MyApp.Mobile.VM.LogOnVM vm) [0x000b2] in D:\Projects\MyAppCore\MyApp.Mobile\MyApp.Mobile\Api.cs:114 }
Just to repeat, the VERY SAME code is running on the physical iphone (and android emulators/phone) perfectly.
Any ideas as to why are appreciated. Thanks.

Answer 1

Following the information Jason provided, I decided to reboot the MAC. And voila! All working again.
I think it may be caused by me starting up 'ExpressVPN' on the PC. I noticed when that is running, the Android won't connect either. However, when I stop it, the Android is OK. But I suspect the Apple never works again until the MAC is rebooted. Not 100% sure that is the reason, but I hope this will help others.
OK - It was NOT the VPN. But rebooting the MAC seems to fix the issue every time.