Cannot load data into Power BI Desktop after transforming in Power Query

The error "Failed to save modifications. Class not registered" usually occurs when Power BI encounters a problem with the data source or the drivers. There can be multiple reasons, and troubleshooting may require various steps. Here are a few things you can try:

1. ODBC drivers: Ensure that the correct version (32 bit or 64 bit) of the ODBC drivers is installed. Power BI is a 64-bit application, and it would need 64-bit ODBC drivers to connect to your MySQL database.

2. Connector/Net: Similar to the ODBC drivers, ensure that you're using the correct version of the Connector/Net.

3. Repair Power BI: Try repairing your Power BI installation. Go to 'Apps and Features' in your Windows settings, select Power BI, and then click on 'Modify'. In the next screen, select 'Repair'.

4. Reinstall Power BI: If repairing doesn't work, try uninstalling and reinstalling Power BI.

5. Update Power BI: Make sure you have the latest version of Power BI installed.

6. Administrator Privileges: Try running Power BI as an administrator.

7. Check for Windows Updates: Ensure your system is up-to-date with the latest Windows updates.

Remember to restart your computer after making these changes, as some of them won't take effect until after a restart.