Firstly, you need to have a proper 2D mesh as pointed out previously. The mesh needs to be fine enough in the x-direction compared with the flame thickness.
You also need to use the "Stiff Chemistry Solver" that can be activated in the "Species Model" dialog box.
Regarding the flame ignition, it's okay to use the ignition model but you can also try simply "patch" a temperature value and the mixture composition corresponding to the combustion products.
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