Resend subscriber confirmation email

Hi wordpress/jetpack family,
I have a wordpress blog and use jetpack for my subscribers.
Some of my friends tried subscribing to my blog in the past and somehow had an error when they clicked on the link in the confirmation email.
But now I tried it myself and asked a few other friends and it works.
So I want my friends who tried subscribing in the first place, but couldn’t, to get the confirmation email again so they can try again. I tried just subscribing to their email on the blog again and they do not receive a ne confirmation email…
Any ideas ?
Thanks ??

Btw wordpress version: 4.9.7
jetpack: 6.1