Email not received by many subscribers

We are getting a lot (not all – it works for many) of subscribers who complete paypal process but then tell us they never received any login info even though that is setup on the WP membership email settings https://prntscr.com/eid9yd https://prntscr.com/eida8s. We thought maybe it was a email domain issue so we tried different email address in here but that did not work. Is there anyway you can tell us what might also be the issue and/or how to make readers more aware that they need to look for welcome email with login during paypal signup process?

Thanks!