Can you try specifying the amount in msats?
curl -X POST https://lnbits.mydomain.tld/api/v1/payments -d '{"out": false, "amount": 1000, "unit": "msat", "memo":"testtest"}' -H "X-Api-Key: <my_invoice_key>" -H "Content-type: application/json"
It does work in the sense that it returns a proper BOLT11 invoice, But LNBits seems to convert msat -> sat incorrectly. 10000msat becomes a 100sat invoice amount (should be 10sats).
It's still not an explanation for the OP error message
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It appears that msat is not a valid unit for LNBits, but instead of throwing an error, they just divide amount by 100.
I raised this issue: https://github.com/lnbits/lnbits/issues/2642 Let's see what they respond.
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In the meantime we stopped using msats for lnbits if you want to give it a shot.
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