Gateway appears to be running but some transfers stay in a tobegin state.

The main issue is to avoid having all allowed connections being used by transfers which are staying in a to begin state waiting for a retry.

There are two types of transfers in a tobegin state.
The transfers waiting to be picked up by a remote partner where Gateway is the responder, these transfers do not concern us.
The other possible tobegin state transfers are Initiator transfers that have not yet begun.
That second type of transfer can lead to the Gateway not being able to send more files if not monitored and addressed properly.

An initiator transfer usually stays in a to begin state indefinitely until the transfer is made even if it reaches the maximum retries. You can change that behavior by setting the stop_site_on_max_retry_eached = 1 in the runtime/etc/conffile.ini. For the changes to be applied to the conffile you'll have to stop Gateway, run peluconf standalone rebuild -f and restart Gateway.

That setting will deactivate the remote site concerned by that transfer and the transfer will also go into a canceled state. Any new transfer attempt to this remote site will not be possible. This setting is to avoid Gateway attempting to send the file indefinitely to non responding remote site. Unfortunately it is not possible to have just the transfers themselves being changed to cancelled when the maximum number of retries is reached.

One has to monitor it's to begin state transfers and verify no tobegin state transfers consumes an allowed connection indefinitely.