Update payment method
Open Dilly -> Settings -> Plan -> Manage subscription. That opens your Stripe customer portal where you can add or update the card on file.
Try the subscription again
After updating the card, reopen Settings -> Plan and re-attempt the upgrade. Stripe will use the new card on the next renewal attempt.
Card declined or country mismatch
If Stripe rejects the card for fraud, region, or balance reasons, the bank usually has the detail. Try a different card, or contact your bank to authorize the charge, then retry from the manage screen.
Still stuck?
Email support@hellodilly.com with the email on your Dilly account. We can see Stripe's side and unstick most failures within a day.