Yes, participants whose activation is pending, can reset their password.
The participant can click on 'Sign in' and then on the 'Forgot Password' link in the login screen, and provide the registered email address to reset their password. Participant profile will be activated once they reset their password successfully. Read the article on Password Recovery to understand the user flow to reset a password
Imported participants are sent an activation email to activate their account when you do not nominate a password during import. This email can be sent to them again from the Participant page. Find the participant and click on the Send activation email link alongside the participant name.
Contact our support team if you need any further assistance via chat or email firstname.lastname@example.org