How do I get back to work after a four-year break?

I am 44 years old and took a voluntary redundancy four years ago from the Civil Service where I worked in a variety of departments and as a manager. I have since been running a very small promotional merchandise business, distributing promo gifts to clients. I have to cold call to get clients and do so by attending seminars and or talking to business owners when I go out. I have also had to attend exhibitions to develop relationships with suppliers. I have done all the book keeping and data management and every aspect of running the business on my own. Before my career with the Civil Service, I also worked as a Temp with various Blue Chip companies from Accenture to NCR to name a few. I have an MBA, but straight after I got it I got pregnant. Hence my choice to work for the Civil Service to be able to enjoy some flexibility, so I have not been able to work with my MBA and I appear to have lost my confidence to apply for work with my MBA. I have also done voluntary roles over the years. I have been applying for jobs over the last year, but have not had any interviews nor responses from the recruiters. Can you kindly advise me on what I can do to improve my chances of getting a job? I would like to work in either a marketing/communications role or in buying which I have had some experience of in the past. I have three kids and they are all in secondary school now, so am ready to go back to work. I would like to work in a role where I can make use of my qualifications.