why if I wanna update my Macs it cannot be updated?

You must be connected to the internet to check for updates. Make sure your wi-fi is active or your Mac is plugged into your router with ethernet cable.

If still unable to check, reboot the computer and try again.

The current version of macOS is 12.4 as of May 16.

There are factors:

1 - Like poor Wifi connection

2 - Slow wifi connection

3 - Too many other people downloading at the same time and Apple Severs are overloaded

4 - Software on the computer interfering with the download process including AntiVirus Software

Notation: Disabling the AV Software may or may not solve the issue. Removal of the AV Software may increase the chances of the download to perform as expected.

5 - Running behind a VPN which may increase Packet losses or corruption of the download 

6 - If via wifi too many Other devices using the wifi at the same time reducing the Bandwidth to your computer. 

7 - Best Results are via Ethernet Cable to Router

Follow previous good advise

If still an issue >.

Terminal command below and what is the exact output

softwareupdate --list-full-installers