LGT-92 and ST-Link V2 USB - can't set up connection to send AT commands

Hello everyone!
I’m doing IoT project for my thesis and I bought two LGT-92 trackers. Unfortunately, I can’t update firmware and send AT commands because of the problem with ST-Link V2 connection. I have recent drivers for ST-Link and ST-Link Utility downloaded. I have two versions (big white and small like pendrive). For both i get error message ‘Can’t connect to the target!’. I do everything like in the dragino manual. I deal with this issue since few days, so i will appreciate every help!