If you have multiple Trailhead accounts after a job change, see Trailhead Self-Service Account Merge to combine them.
Once you have access, update your email so you don't lose access again:
To avoid losing access in the future, connect a personal email, Google, LinkedIn, or Salesforce login to your Trailhead account under Settings > Connected Accounts.

We use three kinds of cookies on our websites: required, functional, and advertising. You can choose whether functional and advertising cookies apply. Click on the different cookie categories to find out more about each category and to change the default settings.
Privacy Statement
Required cookies are necessary for basic website functionality. Some examples include: session cookies needed to transmit the website, authentication cookies, and security cookies.
Functional cookies enhance functions, performance, and services on the website. Some examples include: cookies used to analyze site traffic, cookies used for market research, and cookies used to display advertising that is not directed to a particular individual.
Advertising cookies track activity across websites in order to understand a viewer’s interests, and direct them specific marketing. Some examples include: cookies used for remarketing, or interest-based advertising.