[annalex]

There is no dispute that not all understand the Call and consequently not all are saved.

The issue is, how does God call everyone and not call everyone at the same time in the Calvinist framework that denies free will?

For the Church, there is no conundrum:

God made man a free [agent] from the beginning, possessing his own power, even as he does his own soul, to obey the behests (ad utendum sententia) of God voluntarily, and not by compulsion of God. For there is no coercion with God, but a good will [towards us] is present with Him continually. And therefore does He give good counsel to all. And in man, as well as in angels, He has placed the power of choice (for angels are rational beings), so that those who had yielded obedience might justly possess what is good, given indeed by God, but preserved by themselves.

[...]

it is in man's power to disobey God, and to forfeit what is good

[HarleyD]

The issue is, how does God call everyone and not call everyone at the same time in the Calvinist framework that denies free will?

God calls everyone. Everyone hears the message. You can stand on the street corner and quote John 3:16 all day long but it will not do any good and you will see absolutely no fruit from your labor unless God empowers a response in the believer. And of the thousands of people you may quote John 3:16 to, perhaps only one may truly respond. But that one person is who the Holy Spirit opened up their heart to hear the call.
The Preaching of the Gospel and the Work of the Holy Spirit by John Hendryx

Under your free will framework, you would stand out on the corner shouting John 3:16. Everyone who hear the message would make some type of choice. It is up to them. There is no real working of God's Spirit. There is no specific grace to a particular person.

"For the promise is for you and your children and for all who are far off, as many as the Lord our God will call to Himself." Acts 2:39

No one will be in hell because they made the wrong choice.

For the Church, there is no conundrum

This is silliness. There is no conundrum for the Calvinist either. In fact we can explain predestination and election. You can't.