John and Mel have covered 99% of the issues that may cause your problem.
I assume by “probe” that is the thermocouple you have replaced?
The Ultra store does not use a thermocouple, it is fully controlled by the printed circuit board, which powers the gas valve and the ignitor, and detects the flame electronically.
The symptoms suggest the circuit board is unable to detect the flame, so it goes to "lock out"
The appliance uses almost a full circular burner. It is arranged so the ignition starts at one side of the break, and it relies on the gas flame to spread so it progresses all the way round the burner to other side of the break, where the flame detection electrode is positioned.
If the flame does not make fully round the burner, the flame will not be detected and the PCB will time out and go to lockout.
There can be several causes for this type of fault.:-
First of all, lack of gas, blocked air intake or exhaust or failed ignitor Which the OP has discounted
PCB failure
Broken wires
Electrodes corroded or bent or moved
Burner bar obstructed or damaged (older models used to suffer from rusting)
Without first hand inspection we cannot realistically indicate what the actual problem is
As with all gas installations and appliances you should not attempt repairs unless you are fully competent to do so in accordance with the regulations and you have the full suite of required equipment to perform the necessary testing.