Problem: Missing VLANs

The VLAN could be missing if it was:

not created

accidentally deleted

not allowed on the trunk link

When a VLAN is deleted, any ports assigned to that VLAN become inactive

Ports remain associated with the VLAN until you assign them to a new VLAN or recreate the missing VLAN

Recreating the missing VLAN would automatically reassign the hosts to it

Use the show interface interface-id switchport command to verify the VLAN membership of the port.