To test and verify your RSS feed is functioning properly and does not include any non-ASCII characters, you can easily run your new Simplecast RSS Feed URL through a number of feed validators.
First, fetch your full RSS Feed URL from the Sharing page in your Simplecast admin.
If you plan on publishing your show to Apple Podcasts, Apple provides a RSS verification process to the steps of adding a new show. You can see more in their help center under Validate a Podcast.
For non-Apple solutions, you can find an open source feed validator online at Cast Feed Validator.
A quick Google search can also yield you dozens of beneficial resources.