Turn singles and hazard lights do not come on at all, outside or inside

Start by checking the fuses inside and under the hood. The best suspect is the flasher unit. We used to use two cheap, very reliable mechanical flashers. Today we need a very complicated electronic flasher that does both the signal and four-way functions.

I have checked the fuses and already replaced the flasher box.

You need to include that up front so I don't waste your time with what you've already done. What else have you checked? Do you have a digital voltmeter and know how to use it? Can you get to the connector on the back of the signal switch to do some testing?