rtl-sdr and gr-osmosdr

I have installed these using the procedures shown in the wiki. I didn’t see any errors during the installation. The packages are on the computer but they are not listed amongst the sources on GNU Radio Companion. If I type in the terminal rtl_test –t I get: Found 1 device(s): 0: ezcap USB 2.0 DVB-T/DAB/FM dongle

Using device 0: ezcap USB 2.0 DVB-T/DAB/FM dongle usb_open error -3 Failed to open rtlsdr device #0

Any suggestions?

Many thanks,

Al