Same here. Just upgraded routeros to the new 6.44 firmware and got the same “ready to send” status for the one of my L2TP/IPSec connections. This connection based on Ubuntu Strongswan+xl2tpd service. All other Routers that work on old 6.43.12 firmware connecting to this L2TP-server without problems. I think this is a bug in new firmware.
After I’ve downgraded to 6.43.12 - all works fine as always.