This should be an easy quick fix and I'm hoping it wasn't already fixed (I updated from 6.22.2 to 6.24.1 and didn't noticed a change.
I'm getting the following exception when canceling some orders:
One or more errors occurred. (The json serializer threw a System.Text.Json.JsonException exception when deserializing the 'data' property into a sf_ERP_Shopify_Sync_GraphQL.Models.IO.OrderCancelResult. Check the inner exception for more details.) - The json serializer threw a System.Text.Json.JsonException exception when deserializing the 'data' property into a sf_ERP_Shopify_Sync_GraphQL.Models.IO.OrderCancelResult. Check the inner exception for more details. - The JSON value could not be converted to System.Nullable'1[ShopifySharp.GraphQL.OrderCancelUserErrorCode]. Path: $.orderCancel.orderCancelUserErrors[0].code | LineNumber: 0 | BytePositionInLine: 76.

So it seems like Shopify is just returning an enum value not in code:
///<summary> ///Possible error codes that can be returned by 'OrderCancelUserError'. ///</summary> public enum OrderCancelUserErrorCode { ///<summary> ///An order refund was requested but the user does not have the refund_orders permission. ///</summary> NO_REFUND_PERMISSION, ///<summary> ///The record with the ID used as the input value couldn't be found. ///</summary> NOT_FOUND, ///<summary> ///The input value is invalid. ///</summary> INVALID, }
Especially after looking at the list of them:
https://shopify.dev/docs/api/admin-graphql/2024-10/enums/OrderCancelUserErrorCode.
I wasn't able to log the full response text before deserializing, so I'm not sure what error code was returned or if even though the API is at version 2024-10 they passing the latest values:
https://shopify.dev/docs/api/admin-graphql/latest/enums/OrderCancelUserErrorCode
Or something.

Let me know if you need more info. We haven't had a lot of time to keep up to date with changes as we are on other big projects currently and this error is not a big deal since it seems to have actually canceled the order just fine after looking at it in the Shopify Admin.