The fact that the PLC is marked as "unknown" is not a big issue. Though it could indicate a break in communications (cable damage, compatibility issues or damage on the CPU port). It becomes an issue when there are more than one "unknown" device is listed.

But do make sure that the CPU you have is a standard CPU. There are some OEM customized CPUs which cannot be configured with "public" software.

I have seen this 'problem' before and could continue without problems. Attempt to continue with your task ignoring the warning.

Hello qwazee

I'm sure the CPU is standard, I'm skeptical about the cable, I want to know the exact reason for this error, so I can fix the problem more easily

What Siemens cable are you using and what type USB adapter. 
I assume you use a serial-USB adapter because a naive COM-port are rare these days.

Hi Henry

I using AMSAMOTION Cable, So I'm wondering if it's the cable or not

I'm sure it's the adapter. Good luck fiddling with the settings to get it working. Can't help you there.

Back in the days I tried AMSAMOTION adapter to (0CB20 clone). They "work" but can also be flaky.
Got a second hand Siemens Multi Master adapter (3DB30) from Ebay and never going back.

Not saying AMSAMOTION is bad. They have plenty other good stuff.
The Siemens adapter's/clones from them I don't trust.

Oh Thank you

Perhaps I can close the matter here