In the cash flow tab two options appear, Overview as QuickBooks Cash. but the cash flow planner is not shown.
Starting your cash flow planning is my priority @Bilal Memon.
The Cash Flow Planner and its related function is available as long as you're logged in to the account with the Master Admin privilege. This feature is not yet available for accounts with multicurrency businesses since this is designed to work well with one account and one currency only.
But if the multicurrency feature is turned off, let's consider logging in to your QuickBooks Online account using a private or incognito window in any browser so we can isolate this issue. To do so: