Everytime I fill out the form for a solo 100% lighthouse run and leave player 2 blank I get an error message stating "You didn't enter enough players" , which is preventing me from submitting the run properly

That's odd. I filled out a test submission leaving player 2 blank and it worked just fine.

Not sure what could be causing that...

Update: Ah I see, I was testing on any%, there must be something in the 100% settings that's causing this. Let me look into it.

Hey try submitting again! I think I found the issue in the category settings. Because we don't separate the co op and single player ILs I have to disable the exact player count setting, which was set properly on any% but not 100%. It's been a while since we've had a 100% submission so thank you for helping me catch this!

Another update: I was able to take the rejected run, remove the second player, resubmit, and then verify it for you! It's on the leaderboard now.