Once you have imported your show, you need to redirect your RSS feed from Simplecast to Acast.
You need your new Acast RSS feed URL. It will be something like https://feeds.acast.com/public/shows/mypodcast
This is your Acast feed URL. Copy it to your clipboard.
Redirect your feed
Log in to your Simplecast dashboard
Choose your podcast, and then go to the Show Distribution settings for your show.
At the bottom of the page, click Advanced Settings
Paste your Acast RSS feed URL into the redirect box
Check the redirect is successful
Open your web browser (like Chrome or Safari) and enter the address of your old RSS feed URL, and hit enter. If the redirect is working, you will be taken automatically to your new feed URL at feed.acast.com.
If you are not taken to this new Acast feed URL, then wait ten minutes, clear your browser cache (or open in incognito/private mode) and try again.