BTCPay Server is not configured
Low-level btcpay-api threw because connection settings are incomplete before any invoice request.
Why this happens
Missing server base URL, store ID, or API key in site settings. Sibling of checkout-not-enabled asserts used higher in the stack.
Diagnose and fix
1. Complete BTCPay Server settings under Payment; save.
2. Enable BTCPay checkout if members should see it.
3. Test connectivity from the app host to the BTCPay URL.
4. Then retry; watch for “did not return a checkout link” if config is partial.