How about you provide some more details for this split-key solution problem? I don't ask for the solution itself, that should be obvious.
What software did you use?
What command line arguments did you use?
Was the solution automatically submitted or did you submit the solution manually?
What address type did you use to collect the solution bounty (see below)?
Did you get some error message or something similar in your log file when trying to collect the solution bounty?
Did you check that your split-key solution actually produces a correct address prefix?
Did you contact the original creator? When I look into the profile of ThePiachu, the user was last active quite recently: 2024-10-12, 18:16:52 UTC. You can also mention him here, like with @ThePiachu, but seriously provide more details for debugging your problem. Nobody here can read your mind!
I once solved one of the former and way easier work items offered, but that was a very long time ago. The bounty payment came swiftly to my provided legacy payment address.
Did you use a legacy address type (addresses that start with 1...) as I wouldn't expect if the site can handle wrapped segwit or native segwit addresses!?