Log in to your account to see if there are any outstanding verification requests. These usually cover:
An identity document
Proof of address
Missing personal or financial details
A banner at the top of your account will tell you what's still needed. It's also worth checking your emails from us, including your spam folder, as we may have asked for something specific to your application.
If you've already sent/uploaded everything we asked for, there's nothing else to do. We'll be in touch once the review is complete.