I **think** I have diagnosed the issue. Here is a callback URL that does not work: https://btcpay989117.lndyn.com/BTC/UILNURL/pay/lnaddress/pedromvpg?amount=1000&nostr=%7B%22id%22%3A%22da4036f7220a39ac48bb6497b1090048f49ee078d8677bec4aef6490f2b95a25%22%2C%22sig%22%3A%22d11193e5e90ce9975447678c43dbc470f5113688b2d008f8b5c539a7afbb9c895c41a30c097c44ccfc6ce26ddae0fed527837c62be8c20b0905cabe17ac9486d%22%2C%22pubkey%22%3A%2297f848adcc4c6276685fe48426de5614887c8a51ada0468cec71fba938272911%22%2C%22created_at%22%3A1743989620%2C%22kind%22%3A9734%2C%22tags%22%3A%5B%5B%22relays%22%2C%22wss%3A%2F%2Fbostr.lightningspore.com%22%2C%22wss%3A%2F%2Frelay-nwc-dev.rizful.com%2Fv1%22%2C%22wss%3A%2F%2Fbrb.io%2F%22%2C%22wss%3A%2F%2Feden.nostr.land%2F%22%2C%22wss%3A%2F%2Fnos.lol%2F%22%2C%22wss%3A%2F%2Fnostr-pub.semisol.dev%2F%22%2C%22wss%3A%2F%2Fnostr.orangepill.dev%2F%22%2C%22wss%3A%2F%2Fnostr.zebedee.cloud%2F%22%2C%22wss%3A%2F%2Foffchain.pub%2F%22%2C%22wss%3A%2F%2Fpuravida.nostr.land%2F%22%2C%22wss%3A%2F%2Fpyramid.fiatjaf.com%2F%22%2C%22wss%3A%2F%2Frelay.current.fyi%2F%22%2C%22wss%3A%2F%2Frelay.damus.io%2F%22%2C%22wss%3A%2F%2Frelay.snort.social%2F%22%2C%22wss%3A%2F%2Fnostr.wine%2F%22%2C%22wss%3A%2F%2F140.f7z.io%2F%22%2C%22wss%3A%2F%2Frelay.f7z.io%2F%22%2C%22wss%3A%2F%2Frelay.primal.net%2F%22%5D%2C%5B%22amount%22%2C%221000%22%5D%2C%5B%22lnurl%22%2C%22https%3A%2F%2Fbtcpay989117.lndyn.com%2F.well-known%2Flnurlp%2Fpedromvpg%22%5D%2C%5B%22p%22%2C%228cd2d0f8310f7009e94f50231870756cb39ba68f37506044910e2f71482b1788%22%5D%2C%5B%22e%22%2C%22b8a8ca5154b2725b6810df191f9d399ede245c0e79fd5bae94a19456711ddc66%22%5D%5D%2C%22content%22%3A%22%E2%9C%A8%22%7D&lnurl=LNURL1DP68GURN8GHJ7CN5VDCXZ7FE8QUNZVFH9EKXUEREDCHXXMMD9UH8WETVDSKKKMN0WAHZ7MRWW4EXCUP0WPJKGUN0D4M8QECJMRCWV ........ and here is a callback URL that DOES work... https://btcpay989117.lndyn.com/BTC/UILNURL/pay/lnaddress/pedromvpg?amount=1000&nostr=%7B%22id%22%3A%226ffa1ef877d86d62c1c7813c42e699e916fe53ccfc277740524a14a8bd25c719%22%2C%22sig%22%3A%2208c4924fc86875a7384a62bbe3eee72165b82789a63a8dacb9bce722a8c23fce638b8339075a4b184f347ec5992dc1f77ca74b649c31613c39f636a7c02bae93%22%2C%22pubkey%22%3A%2297f848adcc4c6276685fe48426de5614887c8a51ada0468cec71fba938272911%22%2C%22created_at%22%3A1743989580%2C%22kind%22%3A9734%2C%22tags%22%3A%5B%5B%22relays%22%2C%22wss%3A%2F%2Fbostr.lightningspore.com%22%2C%22wss%3A%2F%2Frelay-nwc-dev.rizful.com%2Fv1%22%2C%22wss%3A%2F%2Fbrb.io%2F%22%2C%22wss%3A%2F%2Feden.nostr.land%2F%22%2C%22wss%3A%2F%2Fnos.lol%2F%22%5D%2C%5B%22amount%22%2C%221000%22%5D%2C%5B%22lnurl%22%2C%22https%3A%2F%2Fbtcpay989117.lndyn.com%2F.well-known%2Flnurlp%2Fpedromvpg%22%5D%2C%5B%22p%22%2C%228cd2d0f8310f7009e94f50231870756cb39ba68f37506044910e2f71482b1788%22%5D%2C%5B%22e%22%2C%22b8a8ca5154b2725b6810df191f9d399ede245c0e79fd5bae94a19456711ddc66%22%5D%5D%2C%22content%22%3A%22%E2%9C%A8%22%7D&lnurl=LNURL1DP68GURN8GHJ7CN5VDCXZ7FE8QUNZVFH9EKXUEREDCHXXMMD9UH8WETVDSKKKMN0WAHZ7MRWW4EXCUP0WPJKGUN0D4M8QECJMRCWV ..... you can see that the callback URL that DOES work is SHORTER...
Testing zaps for this note… we made six attempts to⚡zap this note, at pedromvpg@btcpay989117.lndyn.com, over a period of 19 minutes. In each case, we found that your lightning address server did not respond correctly. (The failure point was when we did a GET request to your specified callback URL: https://btcpay989117.lndyn.com/BTC/UILNURL/pay/lnaddress/pedromvpg.) Your server did not produce an invoice, thus the zap failed. We recommend that you use a cloud-based Lightning node which is optimized for Nostr zaps, to get your zaps working.
Discussion
I'm confused about the URL, why doesn't it start with pay . sprovoost . nl?
Will look into it more tomorrow(ish) after the conference...
There are two URLs in the Nip-57 dance.... the first URL... https://btcpay989117.lndyn.com/.well-known/lnurlp/pedromvpg .. and then you use the "callback" url provided in this response.... and you shove an entire NOSTR event onto that URL! It's pretty ugly but it works!
And yes, the failing URL shows the error: "Lightning node could not generate invoice with description hash:" ... basically, your lightning node is refusing to generate the invoice because it doesn't like the description you provided.... I think it's because it is too long...