I'm currently having a similar situation with this artist. Lots of delays met with silence. When I do get a response, they're excuses. "My pet is sick", "I've been in war", etc. Meanwhile they continue to post new art pieces regularly.
I haven't even been lucky enough to get a sketch or a WIP, I'm pretty sure absolutely zero progress has been made on my piece and it's been over 8 months since I paid. I'm glad you made this post because it's validating my concerns about this artist. I may have to make my own post about them myself.