Liberty Lost:

Milton thinks of true liberty as that of a will governed only by reason and not by a chain of causation, either internal or external.

With the fall of mankind, this free will fell and became subject to human passions, such that Adam and Eve could no longer choose freely. They still made choices, choosing what they desired, but not good choices since their natures had fallen into depravity.

Their postlapsarian lack of freedom manifested itself in mutual accusations not long after their having eaten from the Tree of Knowledge:

They sate them down to weep, nor onely Teares
Raind at thir Eyes, but high Winds worse within
Began to rise, high Passions, Anger, Hate,
Mistrust, Suspicion, Discord, and shook sore
Thir inward State of Mind, calm Region once [ 1125 ]
And full of Peace, now tost and turbulent:
For Understanding rul'd not, and the Will
Heard not her lore, both in subjection now
To sensual Appetite, who from beneathe
Usurping over sovran Reason claimd [ 1130 ]
Superior sway: From thus distemperd brest,
Adam, estrang'd in look and alterd stile,
Speech intermitted thus to Eve renewd.

Note the subjection of the will by the passions. Adam, intemperate now, begins to accuse Eve, not without some justification, but he ignores his own culpability:

Would thou hadst heark'nd to my words, and stai'd
With me, as I besought thee, when that strange [ 1135 ]
Desire of wandring this unhappie Morn,
I know not whence possessd thee; we had then
Remaind still happie, not as now, despoild
Of all our good, sham'd, naked, miserable.
Let none henceforth seek needless cause to approve [ 1140 ]
The Faith they owe; when earnestly they seek
Such proof, conclude, they then begin to faile.

Eve, in turn, accuses Adam of having neglected his role as her protector:

To whom soon mov'd with touch of blame thus Eve.
What words have past thy Lips, Adam severe,
Imput'st thou that to my default, or will [ 1145 ]
Of wandring, as thou call'st it, which who knows
But might as ill have happ'nd thou being by,
Or to thy self perhaps: hadst thou been there,
Or here th' attempt, thou couldst not have discernd
Fraud in the Serpent, speaking as he spake; [ 1150 ]
No ground of enmitie between us known,
Why hee should mean me ill, or seek to harme.
Was I to have never parted from thy side?
As good have grown there still a liveless Rib.
Being as I am, why didst not thou the Head [ 1155 ]
Command me absolutely not to go,
Going into such danger as thou saidst?
Too facil then thou didst not much gainsay,
Nay, didst permit, approve, and fair dismiss.
Hadst thou bin firm and fixt in thy dissent, [ 1160 ]
Neither had I transgress'd, nor thou with mee.

Adam now reponds in hot anger:

To whom then first incenst Adam repli'd,
Is this the Love, is this the recompence
Of mine to thee, ingrateful Eve, exprest
Immutable when thou wert lost, not I, [ 1165 ]
Who might have liv'd and joyd immortal bliss,
Yet willingly chose rather Death with thee:
And am I now upbraided, as the cause
Of thy transgressing? not enough severe,
It seems, in thy restraint: what could I more? [ 1170 ]
I warn'd thee, I admonish'd thee, foretold
The danger, and the lurking Enemie
That lay in wait; beyond this had bin force,
And force upon free Will hath here no place.
But confidence then bore thee on, secure [ 1175 ]
Either to meet no danger, or to finde
Matter of glorious trial; and perhaps
I also err'd in overmuch admiring
What seemd in thee so perfet, that I thought
No evil durst attempt thee, but I rue [ 1180 ]
That errour now, which is become my crime,
And thou th' accuser. Thus it shall befall
Him who to worth in Women overtrusting
Lets her Will rule; restraint she will not brook,
And left to her self, if evil thence ensue, [ 1185 ]
Shee first his weak indulgence will accuse.

Whence Milton interjects:

Thus they in mutual accusation spent
The fruitless hours, but neither self-condemning,
And of thir vain contest appeer'd no end.

I think that Milton handles this entire scene with brilliance. What couple has not, albeit with less eloquence, fallen into such a lovers' quarrel? Crucially, neither Adam nor Eve is self-condemning, for they lack the freedom to do so.

Lacking that, they can never repent.