Getting that first job in a new profession can definitely be challenging. Certification programs for BAs usually require work experience (such as the CCBA and CBAP), so won't help you at this point in your career.

The first step is to evaluate the skills that you have against those required for entry level BA. This will help you re-work your resume to highlight the relevant skills, and identify gaps for skills that you may need to acquire. The Business Analysis Book of Knowledge (BABOK) lists the 6 knowledge areas for BAs - here is a Modern Analyst posting with links to an online version of the BABOK:

http://www.modernanalyst.com/Community/ModernAnalystBlog/tabid/181/articleType/ArticleView/articleId/1341/BABOK-20-Free-DownloadAccess-V2.aspx

Entry level skills usually involve some combination of facilitation, communications, and requirements analysis. Requirements analysis skills and associated tools and techniques are probably the biggest gap coming from a sales career. As you're finding, it's hard to get into any BA role without some training or experience in these areas. You might look into training options to pick up missing skills, if that is something that you're wiling and able to do. Another option might be to look for another type of role that more closely matches your current skills, within an organization that offers opportunities to build skills and move into BA roles. For example, you may be able to find work in a software / product trainer role, that would leverage skills you have and build your analysis skills and software product knowledge - then work on opportunities to transfer into a junior BA position within that company. Many organizations are more willing to give BA roles to employees with less experience than a new hire, simply because they already have some level of confidence in the employee's abilities. So you might look at broadening your job search - but look for companies that are willing to support your professional development and career growth.

Sandy