Not blinking is more an "indicator" (sorry for the pun) of something wrong with wiring or bulb or connection to the base. Cheapest is to replace bulbs to see if the blinking starts. Then check the continuity of the ground to the bulb which does not light. Wire-in a temp replacement to see if the side starts blinking. If it does, then problem is with either wiring or connection to the base.
My 80 CX500c left turn signal did not blink when I bought it some time ago. I have a Fetter Windjammer 4 fairing. The ground connection to the front left bulb base had broken. Soldered it back, and all worked. But not until I fought and fought with the SOB. As an annoyance, when the ground was still bad, the lamp lit up, but that side would not blink.
Montana Clifford