My orders kept being canceled by Amazon

I’m a new seller on Amazon but have been selling on other platforms for a few years without any issues. Since I started selling on Amazon last month, I have been very frustrated. At first I discovered I am not qualified to sell most brand name products, meaning I can’t even submit invoices or LOA to become ungated. Seller support doesn’t know what happened. Then I turned to private label products. I was rejected by Brand registry without a clear reason and my case has been left open for quite a long time. Now I have launched a private label products with ads running. All my orders are pending. Then I started to see my orders canceled without a reason. I’m worried new orders would be canceled soon as well. Seller support told me Amazon canceled them but doesn’t know what happened. What should I do? I feel I lost control of my business. Should I switch to FBM before the issue is resolved?