Hello.
Can you give me please the version 12.9 dll cplex
For CPLEX 12.9 you need to download a CPLEX for AMPL version between 20190312 and 20190908 https://dev.ampl.com/solvers/cplex/changes.html#id18. You can download that from https://portal.ampl.com/user/ampl/download/cplex/list if you have an activate license for CPLEX from us.