What quantities do you see on their portal? I'm guessing the maximum you see is 3, 5 or 10, which makes running an online store impossible (eg, you can't accept an order for 100 flash drives if your site doesn't know that there are more than 5 available).
BTW, even as a Pty Ltd (I never traded as a sole prop) Frontosa rejected my account until I had references elsewhere. I'd been dealing with Frontosa at previous places of employment and my dad's account since the very early 2000s and that wasn't enough.
I started with Corex and Rectron - I have a friends at both who got me in. Rectron had a condition that I meet their trade requirements for the first three months, which at times meant selling at or below cost as items were available elsewhere at lower prices and I was not able to be competitive by adding anything to their price.
What I have learnt is that a solid business plan, no longer than one page but outlying your plans for growth and what will make you successful, financial predictions, your advertising and marketing avenues, your potential market size, your target market, a market analysis addressing your competition and what sets you apart from everyone else, supporting documents if available, etc gets you a LONG way.
Being a semi-decent reseller is something that takes a good 80+ hours per week. I'm working in the background as I type this reply, which is a typical weekend for me

Thankfully I have an understanding wife.
A few other things that may count in your favour are:
References from other suppliers
A proven track record - be this reviews on Hello Peter, a Facebook following, etc
VAT certificate
Reseller TV license
BEE certificate (this has been and will continue to be a major stumbling block for me)