diff --git a/src/FluffySpoon.AspNet.LetsEncrypt/LetsEncryptRenewalService.cs b/src/FluffySpoon.AspNet.LetsEncrypt/LetsEncryptRenewalService.cs
index 3d0460f..dab6d21 100644
--- a/src/FluffySpoon.AspNet.LetsEncrypt/LetsEncryptRenewalService.cs
+++ b/src/FluffySpoon.AspNet.LetsEncrypt/LetsEncryptRenewalService.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 using System.Security.Cryptography;
 using System.Security.Cryptography.X509Certificates;
@@ -273,13 +272,14 @@ private async Task ValidateOrderAsync(string[] domains, IOrderContext order)
 
 				var challengeExceptions = nonNullChallengeValidationResponses
 					.Where(x => x.Status == ChallengeStatus.Invalid)
-					.Select(x => new Exception($"{x.Error.Type}: {x.Error.Detail} (challenge type {x.Type})"))
+					.Select(x => new Exception($"{x.Error?.Type ?? "errortype null"}: {x.Error?.Detail ?? "null errordetails"} (challenge type {x.Type ?? "null"})"))
 					.ToArray();
 
-				if (challengeExceptions.Length > 0)
+				if (challengeExceptions.Length > 0) 
 					throw new OrderInvalidException(
 						"One or more LetsEncrypt orders were invalid. Make sure that LetsEncrypt can contact the domain you are trying to request an SSL certificate for, in order to verify it.",
 						new AggregateException(challengeExceptions));
+                
 			}
 			finally
 			{
@@ -287,17 +287,17 @@ private async Task ValidateOrderAsync(string[] domains, IOrderContext order)
 			}
 		}
 
-		private static async Task<Challenge[]> ValidateChallengesAsync(IEnumerable<IChallengeContext> challengeContexts)
+		private async Task<Challenge[]> ValidateChallengesAsync(IEnumerable<IChallengeContext> challengeContexts)
 		{
 			var challenges = await Task.WhenAll(
 								challengeContexts.Select(x => x.Validate()));
 
 			while (true)
 			{
-				if (!challenges.Any(x => x.Status == ChallengeStatus.Pending || x.Status == ChallengeStatus.Processing))
+				if (challenges.Any(x => x.Status == ChallengeStatus.Valid) || challenges.All(x => x.Status == ChallengeStatus.Invalid))
 					break;
-
-				await Task.Delay(1000);
+                
+                await Task.Delay(1000);
 				challenges = await Task.WhenAll(challengeContexts.Select(x => x.Resource()));
 			}