The placeholders
{{name}} is the member, {{company}} is your community, and {{update_payment_url}} is the deep link to that member's specific failed charge. Swap the first two by hand. The third is the one worth automating, because a generic billing link asks the member to go find the problem themselves and most of them will not.
Why day 0, 2 and 4
Day 0 catches the expired card, which is most of them and usually fixed in under a minute. Day 2 catches the member who meant to deal with it and forgot. Day 4 is the last one that can still land before Whop closes the window, and it deliberately offers a pause instead of only asking for money, because a paused member comes back and a cancelled one does not.
There is no day 5 email. The window closes at the end of day 5, so an email sent that morning can arrive after the membership is already gone. Sending it a day early costs nothing and being one day late costs the member.
If you would rather not do it by hand
ChurnGuard watches Whop's payment webhooks and sends these three from your own connected Gmail or SMTP, with the deep link filled in, and stops the sequence the moment the payment goes through. It also tells you at the end of the week which failures recovered and which did not.