Be sure the the headset in in 'Pairing' mode.
When in pairing mode, the light should be flashing red and blue or have a steady blue.
The put most headsets in pairing mode, turn headset OFF, then hold the power button until it goes into pairing mode as discribed above. Then you can discover it with your phone or PC. Pin (pass key) should be 0000 (4 Zeros) or try 1111, 1234, 9999
You can obtain a copy of your user manual by locating the FCCID on the label directly on the device, then then going to the FCC Website - https://fjallfoss.fcc.gov/oetcf/eas/reports/GenericSearch.cfm
Be sure to put the first three characters in the first box and the rest (including hyphens) in the second box.