IoT Edge runtime error 400 after starting VM which was off for 1+ months - azure-iot-edge

Question

I had a working VM running IoT Edge 1.0.10.3 on Ubuntu 16.04 that I had turned off for the past month or so.
Turned it on today to find that:
I can start up all modules ok. They all report running
The runtime response is: 400 -- The deployment configuration is malformed or invalid
Running iotedge check, it doesn't appear that there's any errors
when I try to set modules, under IoT edge Modules: There are no listed IoT Edge Modules
also I'm getting the following error in the EdgeHub logs:
<4> 2021-01-19 22:27:12.834 +00:00 [WRN] - Error getting edge hub config from twin desired properties
System.ArgumentException: schemaVersion is null or whitespace.
at Microsoft.Azure.Devices.Edge.Util.Preconditions.CheckArgument(Boolean expression, String message) in /home/vsts/work/1/s/edge-util/src/Microsoft.Azure.Devices.Edge.Util/Preconditions.cs:line 73
at Microsoft.Azure.Devices.Edge.Util.Preconditions.CheckNonWhiteSpace(String value, String paramName) in /home/vsts/work/1/s/edge-util/src/Microsoft.Azure.Devices.Edge.Util/Preconditions.cs:line 192
at Microsoft.Azure.Devices.Edge.Hub.Core.Config.EdgeHubDesiredProperties..ctor(String schemaVersion, IDictionary`2 routes, StoreAndForwardConfiguration storeAndForwardConfiguration) in /home/vsts/work/1/s/edge-hub/src/Microsoft.Azure.Devices.Edge.Hub.Core/config/EdgeHubDesiredProperties.cs:line 14
at lambda_method(Closure , Object[] )
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObjectUsingCreatorWithParameters(JsonReader reader, JsonObjectContract contract, JsonProperty containerProperty, ObjectConstructor`1 creator, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateNewObject(JsonReader reader, JsonObjectContract objectContract, JsonProperty containerMember, JsonProperty containerProperty, String id, Boolean& createdFromNonDefaultCreator)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
at Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType)
at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value)
at Microsoft.Azure.Devices.Edge.Hub.Core.Config.TwinConfigSource.GetConfigInternal() in /home/vsts/work/1/s/edge-hub/src/Microsoft.Azure.Devices.Edge.Hub.Core/config/TwinConfigSource.cs:line 97
at Microsoft.Azure.Devices.Edge.Hub.Core.Config.TwinConfigSource.GetConfigInternal() in /home/vsts/work/1/s/edge-hub/src/Microsoft.Azure.Devices.Edge.Hub.Core/config/TwinConfigSource.cs:line 105
What could have happened in the past month of being offline to put the edge into an inconsistent state?

Answer 1

According to the docs, the $schemaVersion that your logs refer to was introduced in 1.0.10. The docs say the property is recommended, but it would seem the runtime requires it. In your comment you included the desired properties, which is missing the $schemaVersion. Try setting the following desired properties:
"properties":{
"desired":{
"routes":{},
"schemaVersion": "1.1",
"$metadata":{
"$lastUpdated":"2020-11-25T18:26:39.4780665Z",
"$lastUpdatedVersion":5,
"routes":{
"$lastUpdated":"2020-11-25T15:03:42.6671499Z",
"$lastUpdatedVersion":4
}
}
}
}