To set up a developer account:
You need to sign in to Oculus with the same account as your device - so if your device has a facebook log in, you need to sign in to Oculus with your facebook Facebook account.
Then follow the steps to create a developer account https://sdq.st/setupSometimes Oculus requires additional verification like credit card details on the account before it will allow dev mode to be activated.
From 1st February 2021 everyone must verify their developer account using one of two simple options.
Developer verification applies to all individual developer accounts, new and existing.
If you have not yet verified your developer account, please follow the steps below before February 1, 2021 to avoid disruption to your account. If your account is not verified by February 1, 2021, you will lose access to your Developer Dashboard, which means you cannot update or access information about your apps. To access your Developer Dashboard after the deadline you will need to verify by following the steps below.
To verify your developer account:
If prompted, login with your Oculus Developer account
Verify your account with one of the two following options:
Confirm your mobile number via SMS two-factor verification
Add a payment method to your account
More info here: https://developer.oculus.com/blog/verify-your-oculus-developer-account-by-february-1/