I have an umbraco site setup (10.2.1) with Umbraco forms installed (10.1.2) and have successfully setup multiple workflows. However when setting up the "Send form to URL" and submitting the form, I get the following error in the logs:

System.FormatException: Unrecognized Guid format.

at System.Guid.GuidResult.SetFailure(Boolean overflow, String failureMessageID) at System.Guid.TryParseGuid(ReadOnlySpan1 guidString, GuidResult& result) at System.Guid..ctor(String g) at Umbraco.Forms.Core.Providers.WorkflowTypes.PostToUrl.AddFieldMappings(NameValueCollection values, List1 mappings, Record record) at Umbraco.Forms.Core.Providers.WorkflowTypes.PostToUrl.Execute(WorkflowExecutionContext context) at Umbraco.Forms.Core.Services.WorkflowExecutionService.ExecuteWorkflows(List`1 workflows, Record record, Form form, FormState state)

I have tried setting up a new form, to see if tha helps, but I just get the same failure each time. Does anyone have any ideas? Thank you Katie