Recent changes mean that Google is now encouraging users to create an ad campaign and enter billing information before using their Keyword Planner tool.
However, there is a way around this.
After logging in, on the 1st screen click the link that says ‘Switch to Expert Mode’ as per the screenshot below:
Then, on the next screen, you need to check the link that says, 'Create an account without a campaign' as shown in the screenshot below.
On the next page, just click save.
Then you will have access to the keyword planner: https://ads.google.com/aw/keywordplanner/home