Via the Fitplan app:
Open the app
Tap Login
Tap Login with Email
Beside the password field tap Help
Enter the email address you use to login to your Fitplan account and tap Retrieve Password
Check your email for reset instructions
Go back to the Fitplan app and sign in with your email and new password
Via Fitplanapp.com:
Click Login on the top navigation menu
Click Forgot Password underneath the login fields
Enter the email address you use to login to your Fitplan account
Click Reset Password
Check your email for reset instructions
Go back to the Fitplanapp.com and sign in with your email and new password

Still have issues logging in? Please send a message via the chat icon in the lower right corner or send an email to support@fitplanapp.com.
P.S.: make sure the email you use to login to Fitplan has no typos