Third level reseller (reseller of the reseller) purchased reseller service plan that was delegated from provider. But not all service plans which are specified in reseller's service template for the plan appeared under new reseller.
Exactly the same plans, that you are delegating to third level reseller, should be delegated to second level reseller as well. If second level reseller does not have these plans then they will not be delegated to third level reseller.
Please delegated to the second level reseller the same plans that you are trying to delegate to third level reseller.