ERROR: DEVICE AE1 NOT FOUND

After you configure LACP (LAG) on the switches Juniper EX3300-24T and Cisco Catalyst 3560 interface is in status down.
If you try to watch statistic (LACP) can see error: device ae1 not found in Juniper. From Cisco side was written
(Gi0/2 suspended: LACP currently not enabled on the remote port) – on remote port doesn’t set up.

Can be solved by setting device-count parameters (set chassis aggregated-devices ethernet device-count 4):

Check: