A non-response is not a no. It is almost always a "later" that never resurfaced. The fix is rarely more nagging — it is removing the friction between intention and tap.
Make the yes take five seconds
Every extra field is a chance to put the phone down and forget. Ask for the reply first; collect the details after the commitment is made. Order matters more than wording.
- Lead with a single, obvious "Will you be there?" choice
- Send the link, not a login — no account should stand between a guest and yes
- Let one gentle automated reminder do the work you used to do by hand