You are trying to connect to an CData source within the K2 Management site under the following category:
Integration >>> Service Instances
Once you are in, you choose to enter the credentials of the instance, selecting the authentication mode and supplying the static credentials, metadata URL etc.
However, once this has been done you are presented with the following error:
"Attempting to connect OData source to K2 VALIDATION The 'Name' attribute is invalid - The value '2_Factor_Authentication' is invalid according to its datatype 'http://schemas.microsoft.com/ado/2007/05/edm:TSimpleIdentifier'"
New fields have been added to the original schema, this may be number fields and fields that may contain underscores.
This is caused by the number fields within the SQL table that the CData api is against. If the number fields are removed, you should be able to successfully create/update the service instance.
This is not a K2 issue but a Microsoft issue .Net C# standard. The reason for this is that the System.Data.Services.Design.EntityClassGenerator is throwing the exception due to it not being able to create a variable that starts with a numeric value.
For further investigation purposes it would be best to log a Microsoft ticket to find a resolution for this issue going forward.