The Most High is not pleased with the offerings of the ungodly: This repeats the meaning of the previous line, with slight variations. Good News Translation says “The Most High gets no pleasure from sacrifices made by ungodly people.” Another possible model is “People who do not worship [or, honor] the Lord Most High cannot please him when they offer sacrifices.” For The Most High, see the comments on 4.10.

And he is not propitiated for sins by a multitude of sacrifices: This means that the Lord does not forgive sins just because people offer sacrifices—even lots of sacrifices.

A possible approach that combines verses 18-19 is:

• If you offer as a sacrifice an animal that you have obtained dishonestly [or, stolen], it is the same as offering a defective animal; the Lord will not accept it. The Lord Most High is never pleased with gifts made by people who do not honor him, or by those who do not keep his Law. No matter how many sacrifices such people offer, the Lord is not going to forgive their sins.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Sirach. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here.