RSS.com is a hosting company and has no influence on whether or not the platforms will accept your RSS.com feed. Some platforms may take longer than others to accept your podcast. For example Apple Podcasts* generally accepts feeds within 24 hours to 2 weeks.
It's important to note, that you should only submit your RSS feed after you have tested it.
For a full list of free RSS Feed validators, please visit here.
If you have not heard back from the platforms after some time, we suggest you contact them directly. Attach your podcast feed to your email to facilitate the work.
*For more information from Apple Podcasts on submitting your RSS Feed please visit: https://itunespartner.apple.com/podcasts/articles/submitting-your-show_testing