If you were represented by a union, your union is your recourse to challenge or appeal your termination.
If your employment was contingent on a condition that you could not satisfy, it is unlikely that you have legal grounds for a claim against your employer. This is true even if the contingency was imposed after you were hired, unless you had a contract or a collective bargaining agreement that provides to the contrary. (That would be an unusual provision.)
The harassment that you cite does not appear from your description to be based on protected characteristics, and so it is likely that these allegations do not result in a sound cause of action against the employer.
No legal advice here. READ THIS BEFORE you contact me! My responses to questions on Avvo are never intended as legal advice and must not be relied upon as if they were legal advice. I give legal advice ONLY in the course of a formal attorney-client relationship. Exchange of information through Avvo's Questions forum does not establish an attorney-client relationship with me. That relationship is established only by joint execution of a written agreement for legal services. My law firm does not provide free consultations. Please do not call or write to me with a “few questions” that require me to analyze the specific facts of your history and your license application and prescribe for you how to get a State license. Send me an email to schedule a paid Consultation for that kind of information, direction, and assistance. My law firm presently accepts cases involving State and federal licenses and permits; discipline against State and federal licenses; and disciplinary and academic challenges to universities, colleges, boarding schools, and private schools. We take cases of wrongful termination or employment discrimination only if the claims involve peace officers, universities or colleges.