Hello guys! Thanks for your response.
I tried all the points mentioned by @Anil_G, with same error. I found this error on Event Viewer: System.Runtime.Serialization.InvalidDataContractException: Type ‘System.Net.Http.HttpRequestException’ cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. If the type is a collection, consider marking it with the CollectionDataContractAttribute. See the Microsoft .NET Framework documentation for other supported types.
I think it could be some network problem, as suggested by @Arvind_Kumar1. Any idea which URL could it be? The error happened even from a home network, when it is supposed everything is open.