I'm currently in the progress of upgrading my v8 site (using this plugin) to V9. I've installed the new package, but I'm only running into a issue, on the existing content, but also when creating a new datatype. The resulting error is as follows:
Newtonsoft.Json.JsonSerializationException: Error converting value "google.maps.maptypeid.roadmap" to type 'System.Nullable`1[Our.Umbraco.GMaps.Models.MapType]'. Path 'mapconfig.maptype', line 1, position 332. ---> System.ArgumentException: Requested value 'google.maps.maptypeid.roadmap' was not found. at Newtonsoft.Json.Utilities.EnumUtils.ParseEnum(Type enumType, NamingStrategy namingStrategy, String value, Boolean disallowNumber) at Newtonsoft.Json.Converters.StringEnumConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer) --- End of inner exception stack trace --- at Newtonsoft.Json.Converters.StringEnumConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, Object existingValue) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id) 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.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target) at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id) 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.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings) at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings) at Our.Umbraco.GMaps.PropertyValueConverter.SingleMapPropertyValueConverter.ConvertIntermediateToObject(IPublishedElement owner, IPublishedPropertyType propertyType, PropertyCacheLevel referenceCacheLevel, Object inter, Boolean preview) at Umbraco.Cms.Core.Models.PublishedContent.PublishedPropertyType.ConvertInterToObject(IPublishedElement owner, PropertyCacheLevel referenceCacheLevel, Object inter, Boolean preview) at Umbraco.Cms.Infrastructure.PublishedCache.Property.GetValue(String culture, String segment) at Umbraco.Extensions.PublishedPropertyExtension.Value[T](IPublishedProperty property, IPublishedValueFallback publishedValueFallback, String culture, String segment, Fallback fallback, T defaultValue) at Umbraco.Extensions.PublishedContentExtensions.Value[T](IPublishedContent content, IPublishedValueFallback publishedValueFallback, String alias, String culture, String segment, Fallback fallback, T defaultValue)