Hey @Alisa Kharis38, congratulations on your podcast launch! Unfortunately we don't support M4A files at this time (we have a list of our supported filetypes here41). If you upload the file to a page on your own website or a service like Google Drive or Dropbox, you could link to it there. Or if you can convert it to an MP3 file instead, you should be able to upload that (using the 'File' option from the content block menu — more info here39 under 'Files').
(Also, you can always get in touch with our support team at firstname.lastname@example.org or via the in-app messenger in your account!) ☺️