I have a flow where a variable is initialised with two email address in our organisation, separated with semicolons, and then further emails are added to the variable, again separated with semicolons.
This variable is then used as the list of approvers to send to.
However each time the flow runs the "Start an Approval" task fails with the error:
InternalServerError. The request failed. Error code: '500'. Error Message: 'BadGateway'.
This messages does not tell me anything useful, so I am unsure as to what the problem is.
Here is my flow:

And here is the "Start and approval" task in edit mode:

What could the problem be?
Thanks for any help,
Richard