Is your fuel dry? Try getting a wood charge bone dry first.
Is your hearth zone getting hot enough? one test would be to put a small chunk of aluminum near the bottom. If you can't melt aluminum, you aren't even close to hot enough. You need red hot coals in the hearth region. After a test run, try digging out the top of the wood charge and looking for a charred region where the pyrolysis begins and then a charcoal region where the cracking and CO happens. You need coals.
Are you introducing too much air? Try using more or less air flow. You can burn off all the producer gas before it can be used. That may be what is happening.
Gasifiers are fiddly things. Keep at it. There are other forums dedicated to gasifiers that may be more helpful to you.