Hi @polyrom3d
When you parent bones together, they can be disconnected. When they are connected the head of the child bone will always be locked to the position of the tail of the parent. Only a disconnected child can translate away from the parent.
In Edit Mode, when you press Alt P, you can ‘Clear Parent’ or ‘Disconnect Bone’.

It sounds like you have cleared the parent instead of disconnecting as @spikeyxxx suggested.
You can reparent it like this.
Select the child > Shift select the Parent > Ctrl P (“Keep offset”)

That should get it to do what you want.
Just so you know, you can also disconnect the child in the bone properties tab.

Just uncheck connected in the relations tab.
Good luck.