Hi @dmagalhaes
I had the same problem as you, it was difficult but with the help of the Support I managed it, so I thought I'd make a practical guide. I hope it can be useful to many people.
Enabling access to the Security Console from the Insight Platform
https://docs.rapid7.com/insightvm/enable-insightvm-platform-login/
This guide will help you enable access to the InsightVM Security Console (On Prem), using the same credentials as the Insight Platform.
1. Within the Security Console, in Administration > Users > Users Management, create a Global Admin user with Username and Email address having the same email address as the user on the Insight Platform, this user will have InsightVM Platform Login (IPL) = No

2. Log out of https://insight.rapid7.com and from the Security Console (On Prem).
3. Using the Global Admin user created in step 1, log in to the Security Console (On Prem).
4. Select "Dashboard" and wait for it to load completely (wait at least 10 seconds for all the Cards to appear).
5. Go to "Home" and wait for the loading to complete (wait at least 10 seconds for all the Cards to appear).
6. Go back to "Dashboard" and wait for it to load completely (wait at least 10 seconds for all the Cards to appear).
A video of the sequence is available https://share.vidyard.com/watch/rkq5Kf1n9ebyFhod8zKAfk
7. Click on your username in the top right corner, and you will see “Enable InsightVM Platform Login”.
8. Confirm and click on “Enable InsightVM Platform Login”.
9. The user used will now appear to have InsightVM Platform Login (IPL) = Yes

10. From now on, it will be possible to enable all future users simply by creating them both within the Insight Platform and within the Security Console from Administration > Users > Users Management, always keeping the email address as both username and email..
11. Once all users are created, go to Administration > Troubleshoot > Run Commands, enter the following command and click Execute
platform-login enable ENTEREMAILADDRESS