i was fired with no reason given

There are 2 means typically that I know of for employees to find out reasons for termination when the employer does not or will not provide one. One is by filing a claim for unemployment benefits. The employer is suppose to respond and state the basis for your termination. The other is to ask to review or a copy of your personnel file, and in doing so, finding a document that states the reason for termination. In Wisconsin, you have the right to review and even obtain a copy (for a fee) of your personnel file within 7 days of a request, which I recommend to send in writing. If the employer does not permit you to review the file, the Equal Rights Division of the Department of Workforce Development will take a complaint and make efforts to get the employer to comply. It usually works. If you suspect the employer terminated your employment based on a prohibited characteristic like gender, age, national origin, or other protected characteristic, then you can file a complaint of discrimination with the Equal Rights Division. But do not delay, as the general rule is that such complaints must be filed within 300 days.