What is the ruling on publishing advertisements for selling TOEFL and IELTS certificates and attracting customers for a commission, knowing that I do not interfere in the details of the process of obtaining the certificate?

If you know that a person falsifies certificates, or if you predominantly suspect it, then it is not permissible for you to cooperate with them or promote their forbidden act; due to the Almighty's saying: "And do not cooperate in sin and aggression." The wage in this case is forbidden. However, if they are promoting an entity that conducts tests to grant certificates to those deserving them, and you do not predominantly suspect that they are granted through fraud and falsification, then there is no harm in you advertising for them and taking a wage for that.