You probably reached or exceeded your account's keyword limit—don't worry—we've got you covered!
If you want to add another project keyword, then you need to either delete the old one(s), upgrade your current subscription, or buy extra keywords to increase your limit.
How to increase keywords limit
Go to your Account Settings
Select Your Subscription and account. You'll be able to upgrade your limits over there.
We hope this article has been useful to you! If you have any further questions or need help, please don't hesitate to get in touch.