Ember has officially wound down its investing options and in-app on-chain wallet. You'll need to transfer the funds out of your BTC wallet by following these steps:
Go to your Profile page in the Ember app
Tap Withdraw
Select your Bitcoin Wallet (not Sat Rewards)
Paste the BTC address you want to send to
Enter and confirm the amount
Follow the prompts to complete your withdrawal
Once confirmed, your BTC will be sent on-chain and you can track it with the transaction ID in a blockchain explorer.