I'm getting an error saying the feature is not included in Quickbooks Online Essentials Subscription when trying to convert to an invoice from estimate. Can this happen?

Converting an estimate to an invoice can be done in QuickBooks Online Essentials, nilakshafreezon.

Since you've encountered an error while doing this, let's perform some troubleshooting steps to resolve the issue. The stored cache can affect the performance of QuickBooks, which can cause unexpected behavior.

We can start by accessing your account via a private window. Here are the keyboard shortcuts: 

• Safari: Command + Shift + N 
• Google Chrome: CTRL + Shift + N
• Mozilla Firefox or Microsoft Edge: CTRL + Shift + P 

Once signed in, I suggest converting an estimate to an invoice. Here's how:

1. Go to the Sales menu and then select All Sales.
2. Find the open estimate, select Create invoice under the Action Column.
3. Add more details to the invoice as necessary, then select Save and close.

For your visual reference, I've attached some screenshots below.

For more details about the process, please see this article: Convert an Estimate into an Invoice in QuickBooks Online.

If the steps work, let's clear the browser's cache. This improves the performance of the program. You can also use compatible browsers. They'll provide you the best and most secure experience with QuickBooks. 

Additionally, the main differences between QuickBooks Online plans are the availability of certain features, the number of users, and usage limits. All of them are already listed here: https://quickbooks.intuit.com/global/online-compare/.

Lastly, I've added an article that'll help you learn how to send invoices over time as you work off an estimate in QuickBooks: Set up and Send Progress Invoices.

I'll be glad to assist you again if you have more questions about managing your sales transactions. Just add the details in the comment section.