Getting lock-out due to no ignition on 90% concord furnace
Can reset by turn system on and off, what might be causing this

No ignition could mean,igniter not working,also could mean limit switch open,, limit switch open could mean furnace overheating, furnace overheating could mean dirty filter,dirty a-coil,slow blowing fan motor, or several more reasons,, check out and let us know.

I cleaned the heat sensor with a damp cloth and replaced the filter, filter did look okay but replaced anyway. It has run for 2 days without shutting down. Thanks