Juniper Networks EX4400 Series switches using “4x25G SFP28 Extension Module” in PIC 2, however the 10g interfaces are not displayed/recognized on the EX4400 switch.

EX4400 switch is not showing 10g interfaces on PIC 2, when checking the interfaces via "show interfaces terse" command. However, as per the “show chassis hardware” output, we see the 10g transceivers being recognized on PIC 2 in the EX4400 switch, we can also see that PIC 2 is using the 4x25G SFP28 Extension Module which is properly installed.

The “4x25GbE SFP+ extension module” operates in 25-gigabit mode by default. 

Configure the following command on the EX4400 switch to configure all the ports in the extension module to operate in 10-gigabit mode:

root@switch# set chassis fpc 0 pic 2 port 0 speed 10g

Now the 10g ports are fully recognized on PIC 2 of the Juniper EX4400 switch.

You can revert to the 25-gigabit mode by using the set chassis fpc 0 pic 2 port 0 speed 25g command or the delete chassis fpc 0 pic 2 port 0 speed 10g command. 

All the ports in the extension module can operate in the same mode only. Do not install SFP+ transceivers and SFP28 transceivers in the extension module at the same time.

https://www.juniper.net/documentation/us/en/hardware/ex4400/topics/topic-map/ex4400-system-overview.html#id-uplink-modules-in-ex4400-switches