Do the cheap easy things first:
-replace bulbs
-check and/or ad ground connections
-check flasher unit on fuse panel
Then read this (and note the hint to do the wiring from the column before committing to steering wheel removal).
https://www.chevytalk.org/fusionbb/showtopic.php?tid/308968/
On my Dad's old work trucks the blinker units could get bonked by your left foot. Sometimes the fuse panels would get cracked if aggressive people in work boots got in there. I recall one truck where I would have to gently apply pressure to the blinker unit with my foot while driving if I wanted signals. Eventually that got fixed...
