The linked-device list shows an authorization relationship; it does not prove that the current Polymorfa connection is online. A stopped number or failed connection can still have a linked-device entry. Check the number's live status and last error as well.
Confirm that you are looking at the intended number and device. If a normal start fails, report its result and time. Do not unlink every device to troubleshoot one connection. If a new pairing is necessary, follow that number's recovery flow and keep all pairing material private.