There are a number of situations where you may be unable to delete batches.
Batches can't be deleted while they are locked. Batches can be left locked when a batch was abandoned without gracefully closing a session. For example, a user is processing a batch and then closes the browser. In this instance the batch will remain locked and cannot be opened or deleted. To rectify this, you can just wait (batch locks will automatically release after a while) or;
Umango uses a Hairpin request to perform batch deletion and deferral. When Umango sites behind a NAT/proxy and tries to reach itself via its public address http/s protocol, this requires the connection to "go out and back in". If this is blocked along the way it will timeout trying, and fail.
As an example, a reverse proxy may handle incoming public traffic that is being routed internally to Umango server as a different hostname and/or port. The request may look like this:
https://umangoserver:443 => http://internalIP:50080
In this example, when Umango tries to make a request back to https://umangoserver:443 the traffic needs to route out and back again (a Hairpin request) and if the outgoing traffic is blocked, due to the http protocol, the port, the server hostname or if all outgoing traffic is blocked, then the request fails.
To resolve this, create a rule for whatever is controlling the network traffic to allow the Harpin request to complete. Alternatively, as a quick one-time fix, with some configurations you can still delete batches by logging into Umango from a browser on the server and using the localhost hostname instead of the configured public facing address.
Link to this article https://umango.com/KB?article=56