1. Double-check your Gravatar/Wordpress email address matches the email you use on PokeBase. Be especially careful if you already had a Wordpress account before coming across Gravatar.
2. Make sure that you've actually set the avatar to display for your email address. It is possible to upload an avatar, but not set it to be active. Follow the two steps in the headings on: https://en.gravatar.com/emails/
3. If you selected a high maturity rating for the avatar you uploaded, then it won't be displayed on PokeBase. Choose the lowest rating.
4. Make sure that you've confirmed your main email address for both Gravatar/Wordpress and PokeBase. If you've added multiple email addresses to your Gravatar account, make sure the one you used on PokeBase is confirmed.
5. It's possible that Gravatar is experiencing server issues, and an unusually long delay is occurring. In the past, people's avatars have eventually displayed after many hours. Some more patience might be enough.