Here’s what I send. Modify for your needs.
Hey Brave Stumbler!
Please do me a huge favour and double check that your payment info is up to date in Patreon. I want to continue being in communion with you through this community, so take a moment to make sure all is up to date on your end. Can you take of this by [insert a date that 3-5 days after you send this message]?
If you’re having issues updating your card, visit the Patreon help page. Here’s the link for your convenience:
patreon.zendesk.com/hc/en-us/articles/203913769-How-do-I-update-my-payment-information-Or, just pop me a note and I’ll see if I can help.
lee