PropellerAds stopped spending after changing Zones — what should I check?

My Campaign was spending normally before I changed the Zone settings. After modifying the Zones, it almost stopped spending, and the Win Rate has remained at 0.

I have already tried:

• Increasing the CPA Goal bid/target;
• Creating a new Campaign;
• Adding poorly performing Zones to the blacklist;
• Broadening some targeting settings.

However, the Campaign still receives little or no traffic and barely spends.

What could be causing this? Is it related to the bid, overly narrow Zone targeting, Campaign settings, or something else? What should I check or change