No. Under Wisconsin case law, the failure to comply with an administrative code requirement like the twenty minute observation period goes to the weight to be given to the test result, not its admissibilty. In other words, it may form the basis for an argument at trial that the judge or jury shouldn't trust the result, but it won't keep out the test.
Furthermore, even if the test were to be thrown out and the the PAC dismissed, it wouldn't automatically stop the prosecutor from continuing to prosecute the underlying OWI.
The successful defense of these cases is complex, and not every lawyer can handle them. An OWI case is not something a lay person is likely to be able to successfully defend by reading some lawyer's website. You need to schedule an appointment with an experienced defense attorney in your area.
This answer is provided for general information only. No legal advice can be given without a consult as to the specifics of the case.
Failure to comply with the 20 minute observation period cannot result in the case being dismissed. It is an issue that can be brought up before a jury, in a jury trial. If brought up in a jury trial the jury can decide that the test result is not valid. The purpose of the 20 minute observation period, which the officer must certify that he has complied with on the intoxilizer test card is to ensure that the test result is not improperly testing high due to mouth alcohol. Residual mouth alcohol can come from a person burping, or regurgitating, ie throwing up. Sometimes residual mouth alcohol comes from the stomach acid in the stomach coming up into the soft tissue in the mouth and staying there, causing a false high reading on the breath testing machine. The 20 minute observation requirement is to eliminate false high readings due to this residual mouth alcohol. The breath machine has an internal component that is supposed to catch residual mouth alcohol, and flag it, and shut down the machine, indicating an invalid test. It doesn't always work. The state, and prosecutor will argue that there was no residual mouth alcohol, if the machine did not flag it, but it is up to the jury to decide.