During the activation of the GSuite Securlet, it redirects to the Google Workspace Marketplace, and there is no Admin Install option for the Elastica Securlet. Only an Uninstall Option.
This could be due to insufficient rights with the GSuite account. It can also happen if the GSuite Securlet was deactivated and the Elastica Securlet app was removed recently
Verify the GSuite admin account being used for the Activation has sufficient rights. See GSuite Securlet documentation.
If the Elastica Securlet was removed from GSuite for any reason, specifically to clean up a previous GSuite Securlet activation, it can take over 24 hours for the Google Workspace Marketplace to know the Elastica Securlet app was removed. Wait another day to do the reactivation.