I want to downgrade from essentials to simple start, but it tells me I can’t.

I appreciate you posting your concern here in the Community space, Kari.

I'll further assist you in downgrading your subscription.

Beforehand, have you encountered specific errors while doing the process? There are times when an error occurs when downgrading your subscription if there are turned-on features available in your current plan and if there are connected third-party apps.

I recommend turning off features such as the inventory and recurring transaction templates and disconnecting the apps.

Once you're ready to downgrade, here's how:

1. Sign in to your QBO account as a primary or company admin.
2. From Settings, choose Subscriptions and billing.
3. Ensure your payment info is up to date.
4. In the QuickBooks Online section, select Downgrade your plan.
5. Review the available plans and then click Choose Plan.
6. Follow the onscreen steps to downgrade your plan.

Otherwise, If you currently have the multicurrency feature enabled, you won’t be able to switch to QuickBooks Simple Start.

Learn more about managing your QBO plan by checking out this helpful reference: Upgrade or downgrade your QuickBooks Online edition.

If you want to cancel your QuickBooks Online account, I'll provide you with this article you read through for a detailed process: Cancel your QuickBooks Online subscription or trial.

If you need more information about managing your accounts, feel free to comment below. I'll be standing by for your response. 

@karijean 

Did you enable the multi currency feature?