iPad problem with premium subscription

Can you help me solve this problem? I purchased premium through my Apple account. Sometimes when I turn on the app, the app shows that I am a free user. Then I give a premium membership and it says that I have already purchased it and it loads the payment and nothing happens. I use it for my business and it is really getting on my nerves. If it is not solved, I want a refund because it is broken and I cannot issue invoices and I am losing money.
