Exchange 2016 OWA / ECP issue : ASSERT: HMACProvider.GetCertificates:protectionCertificates.Length

[Owa] An internal server error occurred. The unhandled exception was: Microsoft.Exchange.Diagnostics.ExAssertException: ASSERT: HMACProvider.GetCertificates:protectionCertificates.Length<1 at Microsoft.Exchange.Diagnostics.ExAssert.AssertInternal(String formatString, Object[] parameters) at Microsoft.Exchange.Clients.Common.HmacProvider.GetCertificates() at Microsoft.Exchange.Clients.Common.HmacProvider.GetHmacProvider() at Microsoft.Exchange.Clients.Common.HmacProvider.ComputeHmac(Byte[][] messageArrays) at Microsoft.Exchange.HttpProxy.FbaModule.SetCadataCookies(HttpApplication httpApplication) at Microsoft.Exchange.HttpProxy.FbaFormPostProxyRequestHandler.HandleFbaFormPost(BackEndServer …