The 4 ways and brakes lights work--- so that rules out many things.
I'm thinking the TS flasher is not powered (blown fuse).
As a test try to swap the TS flasher with the 4 way flasher.
Also test for voltage at the TS flasher.
Remember the TS require the ignition to be ON. While the 4 ways and brakes are hot-at-all-times.
See attached schematic of typical TS system.