Gas fireplace not lighting
You indicated that you replaced the igniter/flame rod and that you're getting 29v to the igniter. That 29v should cause the igniter to glow red and the smart valve should sense this and open the valve to the pilot releasing the gas flow. The fact that you're getting 29v to the igniter indicates that the transformer is working properly. Since you have voltage but the smart valve is not releasing gas to the pilot your only recourse is to replace the smart valve. According to Honeywell the smart valve cannot be repaired but must be replaced in it's entirety.
Edit: I did more research on your model. At this point I'm convinced that the smart valve needs to be replaced. I am attaching a link to a troubleshooting guide from Honeywell that supports that diagnosis. It's for the 40&quot; model instead of the 36&quot; but the ignition mechanisms are the same. The ignition is electronic not millivolt. Although you're getting a 29v output to the igniter it isn't operating the gas valve which is in the smart valve. The Honeywell part number is 62L1801. Below is a link to the part - it's expensive. You might try used.
https://www.allpartsinc.com/catalogsearch/result/?q=Honeywell+62L1801
https://www.manualslib.com/manual/170931/Superior-B-40ren.html?page=15#manual
Replacing the gas valve will obviously entail redoing the gas connections. If you're uncomfortable doing that you may want to bring in a technician.