Do I Need an SSL/TLS Certificate to Use MemberPress?
No, use of a security certificate is not required, though it is recommended.
Security certificates are what web browsers look for to place the green lock icon on the left of a site URL.
Seeing that may help your customers feel more confident about entering their personal data into your site.
For the exact SSL/TLS security requirements of those gateways, please contact their support directly.
Note: It is best to avoid security systems that allow you to selectively add SSL/TLS to your site. This can cause issues with the WordPress Login cookie that is discussed in greater detail here.