Before you actually submit your feed to any platform, please check your podcast to ensure that you have followed all requirements needed.
1. Change your Cover Art Image (Max image size 400kb, 1600x1600 JPG or PNG)
2. Upload at least one podcast episode (try to compress your file, for example use a Mp3 format)
Before submitting your RSS feed, you'll need to make sure it's valid. Here is a list of free RSS Feed validators: https://help.rss.com/en/support/solutions/articles/44000641875-how-do-i-validate-my-podcast-rss-feed-