The https://insight.rapid7.com/ platform credentials are managed through that platform, however, the credentials for your InsightVM URL (full-stinkbug), are located at the below link.
You can also get there by logging into the Rapid7 platform > Click the 9 dots at the top left → Click InsightVM → Click on the “Administration” button on the left (the logo looks like 3 rows on a to do list) → Click on “User Management” at the top left.
This is where the InsightVM credentials are stored. You won’t be able to edit your currently logged in credentials, but you may be able to make a new user with all permissions, log in with their account, then change your password.
Anytime. If you have any more questions, feel free to open a new ticket with the appropriate title so that others can search against it for future references.