The new Patreon one at the CV Arena? You have to have met Bloodthirster before by getting to the Ferron Hangout event at the Gym. And then the CV Arena event has variant scenes depending on if you're handsome or cute. If you want to have the sex scene with him, then you need to have cute looks, which will require certain drinks from Foxxucks. And you'll need to have done his prior sex scene in the Gym.
The Wiki page has details on the event and the variations, it's the one titled Angry Buff Guy Coming Through: https://summoned-by-accident.fandom.com/wiki/CV_Arena
For which drinks from Foxxucks to take to make you cute, see here: https://summoned-by-accident.fandom.com/wiki/Foxxucks
Now if you're instead meaning his event at the Gym that's in the public version, which is titled Sweaty Angry Orc Pump, then you'll still need to have met Bloodthirster in the Ferron Hangout and you'll still need to be Cute. But, additionally, you'll need to have turned on the Musk flag, so his sweat draws you to him.
Details on that event found here: https://summoned-by-accident.fandom.com/wiki/Gym
And you can turn the Musk flag on from the Forgotten Towel event in the Gym.
I just double checked the requirements and, no, there's just the three flags for it. Have to have met Bloodthirster in the Ferron Hangout, must have Musk flag on, and must have Cute appearance.
Are you absolutely sure your appearance is Cute? Under the Appearance tab on the sidebar (which only shows up after you've leveled up at least once), does it say "Your looking rugged and quite masculine." or "Your skin is as smooth as you are as cute."
If the former, then you're not in a cute state and you need to drink the appropriate drinks from Foxxucks until your cuteness is higher than your handsomeness, which will change the appearance text to the latter version.