this one helps. One of the reasons could be that you are exceeding the maximum weight limit or passing an incorrect value for the CM and KG units. Add a lower value for the weight, start with 10 KG.
How to add Charges to shipping method in Magento
By : Yassine Jamai
Date : March 29 2020, 07:55 AM
wish of those help More than likely your going to want to just create an observer to do what your are needing: You'll need to look around for the proper observer event to hook into, however here is an example observer method: