Promethease supports MyHeritage's original raw data format (pre-2019) as well as from their new data format.
When logged in to your MyHeritage account, go to the DNA section and from the pull-down options for that section choose "Manage DNA kits".
When you are looking at the list of DNA kits in your MyHeritage account, there will be three gray dots to the right of each kit.
Clicking the three dots to the right of the file you wish to download data for, and you will see the "Download kit" option, which is what you should select. Click 'continue' and agree to the information provided, and then MyHeritage will send an email to you including instructions and a direct link to your raw data file for downloading.