Jesus paid for every sin but unbelief.
Yes, but then we have that sticky situation o
f Romans 1 about
the people under HIS wrath knowing the truth about HIM and the gospel but refusing to cease their sin because they love their sin more than the truth. This means that knowing the truth about HIS reality doesn't automatically bring one from a soul destroying unbelief to a to saving faith...
Faith is a trust and a hope in a claim to be true without proof,
Heb 11:1, etc.
If you decide to withhold your faith until you have seen proof of the truth, then it is too late or the inevitable suffering of hell would bring even the devil to faith but he won't / can't.
For a person free of the enslavement to sin, that is, with their free will intact, they are not coerced by hearing the claim of the truth to believe or disbelieve the truth - it is open to each person's desires of what he thinks will bring him the most happiness. Saving faith can only arise before the proof is seen because once the truth is proven, the person is coerced by his knowledge of the future, by not his own deepest desires, to choose to accept the truth. Accepting a proposal of marriage is special; that way.
Satan
et al refused to put their faith in YHWH's unproven claims of HIS divinity and the gospel. GOD wanted us to accept HIM on faith because that is the only proof HE had that we really wanted to live with HIM in a holy marriage, living within the confines of HIS righteous nature. HE didn't want to have people agree to be HIS Bride
only because HE overwhelmed them with HIS power...HE wanted to marry those who heard HIS claims and who responded by thinking,
"Yes, I want to live like that with HIM so I will accept HIM as my LORD and GOD and saviour from all sin and then see how this unproven hope proves out!" uncoerced by seeing / knowing the proof of the truth and the inevitable future.
Saving faith came before
the proof of HIS divinity and eternal power because after that proof was given as per
Romans 1, no one had a freedom of will to change their minds about these issues - they knew the future and were coerced by that knowledge and a coerced decision does not arise from the free will hopes of the person but from outside of his desires.
GOD is not a Borg willing to have a Stepford wife so HE will not marry anyone who has to be coerced by the truth to marry HIM, but will only marry those with the desire to receive who HE is what HE is offering without proof that HE can deliver.
So, since the creation of the physical universe proved HIS divinity and eternal power and Christ's death on the cross proved His ability to save of His sheep gone astray, Satan
et al are not saved by knowing the full truth of GOD but, because they refused to trust by faith, an unproven hope before they saw the truth, they are now under HIS wrath,
Rom 1:18, condemned already,
Jn 3:18.