@kent79 from openweathermap.com:
"Dear OpenWeather user,
We would like to inform you about our plans to complete the migration from One Call 2.5 to One Call 3.0 that started 2 years ago. In line with this, access to One Call 2.5 will be finally closed in June 2024.
One Call 3.0 provides you with significantly advanced business-demanded features such as a minute forecast for 1 hour, 4 days forecast for any timestamp, a daily forecast for 8 days, including a human-readable summary, historical data (45-year archive) for timestamps, and with daily aggregation, 1.5-year long-term forecast with daily aggregation, and others."
So V2.5 is only working because openwaethermap didn’t fully shut it down even the deadline is over. It can happen any day.