Sender dropdown exceeded

There are more Senders on the account than can be shown in the Sender dropdown (approx. 10).

Troubleshooting steps

Use a partial number search to find the Sender:

Sender is already attached to a Group

If the Sender is unselectable (greyed out), it is already attached to a different Group (generally shown next to the Sender).  A Sender can only be attached to one Group.

Troubleshooting steps

Detach the Sender from the current Group before adding it to another Group (see Create and manage Groups).