Check to see if the dryer is heating properly throughout the cycle. If the dryer heats initially but then does not continue to heat, you could have weak gas valve coils (kit part 279834). If this describes your failure, you can order that kit from the
website. Here is a direct link for that gas valve coil kit:
Valve Coil Kit
. You can
unplug the dryer and shut off the gas supply
then remove that bottom front service panel as shown in the image below to access that gas valve assembly. Here is a link for a video that shows how to replace those coils on a similar type of dryer:
Gas Valve Coil Kit Replacement
If the dryer does not heat at all, you could have a blown thermal fuse or a number of other failures in that heating system. If the dryer heats properly, then your symptoms point to a problem with exhaust air flow even though you indicated that you checked that issue. You may need to check the entire vent duct system to the outside of your home in that situation.
These tips may help you get started with the diagnosis and repair of this drying problem. If you need more assistance, reply with additional details.
If you get to the point where you need to have a service technician diagnose and repair this drying failure, you can schedule service through this link:
Sears Home Services