Layer one is the link itself, the E1 signal.
Make a loop to the provider, using a patch cord, or a piece of coaxial cable,depending on what interface they provide.
That should clear the “layer one” alarm, only to bring up the “layer 2” alarm.
Do the same on your side, towards the gateway. Trought a loop back to the gateway, retrieve the alarms and see if the LOS clears when you do the loop.
Do you know that you need a “baloon” betwen the provider and the gateway?????
Unless the provider is giving you the E1 already on a RJ45 connector.