I've been subscribed to Kagi ever since this was launched, but I always found the payment flow confusing. (Maybe this applies to all your prepaid options, not just bitcoin?)
Most recently I got a popup saying my prepayments ran out. So I visited the opennode link and added a year's worth of funds, and they showed up in my account balance, but didn't apply to my current subscription. The guilt-inducing popups continued and I couldn't find any way in the billing/settings to actually use those funds. In the Stripe flow, the only option was to use a credit card, so I bailed. Finally today my subscription was canceled for nonpayment, Only now did my account balance show up in the Stripe flow, so I was able to (re)subscribe. So basically I was using Kagi for free the past few days, although I feel bad because I wasn't trying to!
I got it figured out in the end so I don't need support or anything. I'm just leaving some UX feedback in case you find it useful.