Your account may be pending for one of two reasons.
If you're an established customer who has previously run ads and now have your account in pending status, then you need to add a payment method. Once you add a payment method, your account will become active.
If you're a new Bing Ads customer, please note that your account can remain in pending status for up to 3 days after new setup. Make sure that you've completed the following items in order to establish your account:
Your account will remain pending if you skip any of those items. If you've completed the tasks and your account remains pending more than 3 days after initial setup, please contact Bing Ads Support for further assistance.