The pedal won't be firm if you don't get the air out of alll four corners. You could have gotten some debris in the line when it was apart and that is blocking that side.
I would start by completely removing the bleeder bolt from the left front slave cylinder. If fluid comes out, get a new bleeder bolt and see if the issue is fixed.
Next, unhook the left front soft line from the slave cylinder. Do you get fluid out? If so, the issue is with your slave cylinder. Clean, rebuild, replace as you see fit. Check to see if the issue is fixed.
Next, unhook the soft line from the hard line. If you don't get fluid here, it is the hard line or the MC. I don't have a 41 FAM in front of me, but I believe both front brakes share a single hardline/port so the issue is likely downstream of that.
