The verse "However they did not listen, but they did what they did before" from 2 Kings 17:40 refers to the Israelites' continued practice of idolatry and pagan customs, even after being warned and taught about the true God. Let's break it down:

"However they did not listen...": This highlights the Israelites' disobedience. Despite being instructed, likely through prophets or priests, to abandon their idolatrous practices and worship the one true God, they ignored the message.
"...but they did what they did before.": This emphasizes their persistence in their old ways. "What they did before" refers to their established patterns of idolatry, worshiping false gods, and engaging in practices that were contrary to God's laws and commandments.

In the broader context of 2 Kings 17, this verse is part of a narrative explaining the reasons for the Northern Kingdom of Israel's downfall and exile. God had sent prophets to warn them to turn away from their sins, but they refused. This verse underscores their stubborn refusal to repent and their continued adherence to pagan practices, which ultimately led to God's judgment.

Essentially, it means:

The Israelites were told to stop their sinful practices and worship God.
They ignored the warning.
They continued to worship idols and do the same things they had always done.

This stubborn refusal to change is presented as a key reason for their exile and the loss of their land.