Why am i unable to post a transaction. under a category? It tells me transaction not accepted

That's unusual, crystalcleanhawa,

Your browser's cache might be the reason why you're unable to categorize a transaction.

Let's start by opening your account in a private or incognito window. This mode doesn't keep track of your searches. You can use the keyboard shortcuts below: 

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Safari: Command + Option + P

Then, go to the Banking page and try to categorize the transactions. If you can select a category, then let's go back to your regular browser and clear its cache. Clearing cache improves your browser's performance. Please make sure to close and re-open your browser afterwards.

Alternatively, try using a different supported browser.  

I've got this article on how to categorize banking transactions: Categorize and match online bank transactions in QuickBooks Online. 

Feel free to reach out to me again with any QuickBooks-related questions you may have.