See IRS Regulation 1.162-5

In general, money spent to qualify for the entry-level minimum requirement for a job, or for a new job is not deductible.

To deduct business expense, the expense has to be "ordinary and necessary". From IRS point of view, the money spent to qualify a new job is personal expenses. In other words, you choose to spend the money. These are not "necessary and ordinary" business expenses.

Of course, if you can justify somehow that this is "ordinary and necessary" for your existing business, then go ahead and claim it. But be prepared when you get audited.