Celica Forums General Discussion Interior Problem with amp bypass and new stereo

So I decided to install a new HU in my celica and I bought the bypass harness and wired everything correctly. Checked about 20 extra times to be sure. And I’m getting no audio from the left side at all. So I hooked up my stock HU to see if I have the same problem and then it went away and both side speakers were working again. So I figured okay it might e a faulty HU since I bought it used. Then I bought a brand new pioneer HU and the same thing happened!! I even tried tapping into the factory harness to get power to left speakers and still nothing. How is it that my speakers only work with the amp and stock HU ?? Much help is needed . I’ve stressed for about 3 days over this and I have no radio in my car please help