en_tn/act/16/19.md

her masters

"the owners of the slave girl"

When her masters saw that their opportunity to make money was now gone

It can be stated clearly why they no longer hoped to make money. AT: "When her masters saw that she could no longer earn money for them by telling fortunes" (See: rc://en/ta/man/translate/figs-explicit)

into the marketplace

"into the public square." This is a public place of business, where buying and selling of goods, cattle, or services takes place.

before the authorities

"into the presence of the authorities" or "so that the authorities could judge them"