You'll get this message prompt when you've selected an asset account with detail type inventory as your header or distribution account.
Since you've tried selecting other account type, you'll want to access your account using a private window. This way, we can identify if its browser related or not. Just press CTRL+SHIFT+N for Chrome.
Once done, create a transaction with the correct account type again.
If you're able to save, go back to your regular browser and clear your browser's cache. Deleting your cache will free up storage space of your browser.
Please contact our support if none of the above recommendation works. Here's how to reach us:
You can also visit our page about income and expenses for some help articles for your future tasks.
Feel free to swing by anytime soon if you have other questions.