If you want to use MySQL database for storing users, but failed to connect to MySQL 8.x, maybe you can try the following steps:
1) Stop the Wing FTP Server service.
2) Download this zip file and decompress it into WingFTP's installation folder: https://www.wftpserver.com/bbsres/libmysql.zip
3) Launch the file "VC_redist_2015-2022.x64.exe" and restart the WingFTP service.