I am not clear on what you are asking. The 6906 is of the type referred to as a "Traditional Double-Action" or TDA. Is is that you are wondering why the hammer stays back after a shot is fired (it is supposed to), or that the gun does not fire when you pull the trigger for single-action?

If it is the first there isn't a problem. If it is the second, then something is preventing the dis-connector from engaging the sear properly. This could be caused by something as simple as being dirty, or there could be a piece of debris inside ths gun mechanically interfering with he dis-connector.

Try this. With the gun clear, pull the trigger and hold it fully to the rear while you pull the slide back and let it go forward. It will only take three hands because of the magazine safety, and you will have to have a magazine in the gun unless it has been de-activated. Hold the gun close to your ear and listen carefully. You should hear a faint, but distinct, click when you release the trigger. This is the dis-connector re-setting. If you don't hear a click, and the hammer will not drop when the trigger is pulled, start be thoroughly cleaning the gun. "Gun Scrubber", "Brake Clean", or "Lectro-motive Cleaner", they are all the same, are ideal for flushing guns you don't want to dis-assemble fully. The stocks should be off to do this. Lubricate the gun and try it again. A few drops of oil thoroughly distributed by using an air gun is sufficient.

If cleaning doesn't work it is probably a broken spring.

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Gunsmithing since 1961