Yes, this is the first time I've dealt with something like this, this was last year, I've learned since then and I only make a quick rough sketch before asking for payments now.
I took a commission from someone watching my livestream, it was on the spot and meant to be 1 bust, and then during the middle of the livestream they asked for a second. The attachment is the result of that (NSFW hentai warning), after our last contact they never paid the invoice.
[Mod Edit] From OP when asked about the invoice being canceled: No, I posted about this interaction on the Hentai-Reserve discord after sending the invoice, Arendale went no contact and didn't pay and then other artists on the discord had the same problem with them of non-payment, so I cut my loses.