You put in a few show commands on switches EDGE1 and CORE1 to attempt to...

LACP is a protocol that allows multiple physical links to be aggregated into a single logical link for increased bandwidth and redundancy. LACP must be configured on both ends of the link for it to work properly. In this case, EDGE1 has LACP configured on its uplink port-channel 1, but CORE1 does not have LACP configured on its corresponding port-channel 1. This causes a mismatch and prevents the link from coming up.References:https://www.arubanetworks.com/techdocs/ArubaOS_86_Web_Help/Content/arubaos-solutions/1-overview/lacp.htm