I had this problem and I noticed that it happens because the simulator configuration of the Xamarin app doesn't have the Entitlement.plist reference. Look my Xamarin.iOS.csproj file:
{...}
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|iPhoneSimulator' ">
<DebugSymbols>true</DebugSymbols>
<DebugType>portable</DebugType>
<Optimize>false</Optimize>
<OutputPath>bin\iPhoneSimulator\Debug</OutputPath>
<DefineConstants>DEBUG</DefineConstants>
<ErrorReport>prompt</ErrorReport>
<WarningLevel>4</WarningLevel>
<MtouchArch>x86_64</MtouchArch>
<MtouchLink>SdkOnly</MtouchLink>
<MtouchDebug>true</MtouchDebug>
<CodesignProvision>Automatic</CodesignProvision>
<CodesignKey>iPhone Developer</CodesignKey>
// missing Entitlements.plist reference
</PropertyGroup>
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|iPhone' ">
<DebugSymbols>true</DebugSymbols>
<DebugType>portable</DebugType>
<Optimize>false</Optimize>
<OutputPath>bin\iPhone\Debug</OutputPath>
<DefineConstants>DEBUG</DefineConstants>
<ErrorReport>prompt</ErrorReport>
<WarningLevel>4</WarningLevel>
<MtouchArch>ARM64</MtouchArch>
<CodesignKey>iPhone Developer</CodesignKey>
<MtouchDebug>true</MtouchDebug>
<CodesignEntitlements>Entitlements.plist</CodesignEntitlements> // Entitlements.plist reference
<MtouchLink>None</MtouchLink>
<MtouchInterpreter>-all</MtouchInterpreter>
</PropertyGroup>
{...}
Adding <CodesignEntitlements>Entitlements.plist</CodesignEntitlements> to the simulators config was enough to fix it.
