Problem
System.InvalidOperationException: Could not get algorithm from X509AsymmetricSecurityKey at Microsoft.IdentityModel.S2S.Tokens.X509AsymmetricSignatureProvider..ctor(X509AsymmetricSecurityKey x509Key) at Microsoft.IdentityModel.S2S.Tokens.SignatureProvider.Create(SigningCredentials signingCredentials) at Microsoft.IdentityModel.S2S.Tokens.JsonWebSecurityTokenHandler.Sign(String signingInput, SigningCredentials signingCredentials) at Microsoft.IdentityModel.S2S.Tokens.JsonWebSecurityTokenHandler.WriteTokenAsString(SecurityToken token) at PointShare.SharePoint.PrividerHosted.AddIn.TEST.TokenHelper.IssueToken(String sourceApplication, String issuerApplication, String sourceRealm, String targetApplication, String targetRealm, String targetApplicationHostName, Boolean trustedForDelegation, IEnumerable`1 claims, Boolean appOnly)
Solution
Downgrade httpRuntimetargetFramework to .NET 4.6
Web.config:
<system.web> <compilation debug="true" targetFramework="4.7.2"/> <httpRuntimetargetFramework="4.6.2"/>