Check your public_html/.htaccess file and remove or comment any line beginning with:
AddType application/x-httpd-php
I suggest performing a backup to the file before any changes.
If that doesn't help, contact the support team via ticket to receive priority or use any other method you might prefer. Refer this post to the support team and upload the .htaccess file of your WordPress website (I suggest to rename it to htaccess.txt before sending it).